Fred Drake | 295da24 | 1998-08-10 19:42:37 +0000 | [diff] [blame] | 1 | \section{Built-in Functions \label{built-in-funcs}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 2 | |
| 3 | The Python interpreter has a number of functions built into it that |
| 4 | are always available. They are listed here in alphabetical order. |
| 5 | |
| 6 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 7 | \setindexsubitem{(built-in function)} |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 8 | |
| 9 | \begin{funcdesc}{__import__}{name\optional{, globals\optional{, locals\optional{, fromlist}}}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 10 | This function is invoked by the \keyword{import}\stindex{import} |
| 11 | statement. It mainly exists so that you can replace it with another |
| 12 | function that has a compatible interface, in order to change the |
| 13 | semantics of the \keyword{import} statement. For examples of why |
| 14 | and how you would do this, see the standard library modules |
| 15 | \module{ihooks}\refstmodindex{ihooks} and |
| 16 | \refmodule{rexec}\refstmodindex{rexec}. See also the built-in |
| 17 | module \refmodule{imp}\refbimodindex{imp}, which defines some useful |
| 18 | operations out of which you can build your own |
| 19 | \function{__import__()} function. |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 20 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 21 | For example, the statement \samp{import spam} results in the |
| 22 | following call: \code{__import__('spam',} \code{globals(),} |
| 23 | \code{locals(), [])}; the statement \samp{from spam.ham import eggs} |
| 24 | results in \samp{__import__('spam.ham', globals(), locals(), |
| 25 | ['eggs'])}. Note that even though \code{locals()} and |
| 26 | \code{['eggs']} are passed in as arguments, the |
| 27 | \function{__import__()} function does not set the local variable |
| 28 | named \code{eggs}; this is done by subsequent code that is generated |
| 29 | for the import statement. (In fact, the standard implementation |
| 30 | does not use its \var{locals} argument at all, and uses its |
| 31 | \var{globals} only to determine the package context of the |
| 32 | \keyword{import} statement.) |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 33 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 34 | When the \var{name} variable is of the form \code{package.module}, |
| 35 | normally, the top-level package (the name up till the first dot) is |
| 36 | returned, \emph{not} the module named by \var{name}. However, when |
| 37 | a non-empty \var{fromlist} argument is given, the module named by |
| 38 | \var{name} is returned. This is done for compatibility with the |
| 39 | bytecode generated for the different kinds of import statement; when |
Fred Drake | d6cf8be | 2002-10-22 20:31:22 +0000 | [diff] [blame] | 40 | using \samp{import spam.ham.eggs}, the top-level package \module{spam} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 41 | must be placed in the importing namespace, but when using \samp{from |
| 42 | spam.ham import eggs}, the \code{spam.ham} subpackage must be used |
| 43 | to find the \code{eggs} variable. As a workaround for this |
| 44 | behavior, use \function{getattr()} to extract the desired |
| 45 | components. For example, you could define the following helper: |
Guido van Rossum | 8c2da61 | 1998-12-04 15:32:17 +0000 | [diff] [blame] | 46 | |
| 47 | \begin{verbatim} |
Guido van Rossum | 8c2da61 | 1998-12-04 15:32:17 +0000 | [diff] [blame] | 48 | def my_import(name): |
| 49 | mod = __import__(name) |
Fred Drake | d6cf8be | 2002-10-22 20:31:22 +0000 | [diff] [blame] | 50 | components = name.split('.') |
Guido van Rossum | 8c2da61 | 1998-12-04 15:32:17 +0000 | [diff] [blame] | 51 | for comp in components[1:]: |
| 52 | mod = getattr(mod, comp) |
| 53 | return mod |
| 54 | \end{verbatim} |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 55 | \end{funcdesc} |
| 56 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 57 | \begin{funcdesc}{abs}{x} |
| 58 | Return the absolute value of a number. The argument may be a plain |
Guido van Rossum | 921f32c | 1997-06-02 17:21:20 +0000 | [diff] [blame] | 59 | or long integer or a floating point number. If the argument is a |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 60 | complex number, its magnitude is returned. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 61 | \end{funcdesc} |
| 62 | |
Raymond Hettinger | 74923d7 | 2003-09-09 01:12:18 +0000 | [diff] [blame] | 63 | \begin{funcdesc}{basestring}{} |
| 64 | This abstract type is the superclass for \class{str} and \class{unicode}. |
| 65 | It cannot be called or instantiated, but it can be used to test whether |
| 66 | an object is an instance of \class{str} or \class{unicode}. |
| 67 | \code{isinstance(obj, basestring)} is equivalent to |
| 68 | \code{isinstance(obj, (str, unicode))}. |
| 69 | \versionadded{2.3} |
| 70 | \end{funcdesc} |
| 71 | |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 72 | \begin{funcdesc}{bool}{\optional{x}} |
Guido van Rossum | 77f6a65 | 2002-04-03 22:41:51 +0000 | [diff] [blame] | 73 | Convert a value to a Boolean, using the standard truth testing |
Fred Drake | f96dd83 | 2003-12-05 18:57:00 +0000 | [diff] [blame] | 74 | procedure. If \var{x} is false or omitted, this returns |
| 75 | \constant{False}; otherwise it returns \constant{True}. |
| 76 | \class{bool} is also a class, which is a subclass of \class{int}. |
| 77 | Class \class{bool} cannot be subclassed further. Its only instances |
| 78 | are \constant{False} and \constant{True}. |
Raymond Hettinger | 7e902b2 | 2003-06-11 09:15:26 +0000 | [diff] [blame] | 79 | |
Fred Drake | f96dd83 | 2003-12-05 18:57:00 +0000 | [diff] [blame] | 80 | \indexii{Boolean}{type} |
| 81 | \versionadded{2.2.1} |
Neal Norwitz | 938b7a0 | 2003-06-17 02:37:06 +0000 | [diff] [blame] | 82 | \versionchanged[If no argument is given, this function returns |
Fred Drake | f96dd83 | 2003-12-05 18:57:00 +0000 | [diff] [blame] | 83 | \constant{False}]{2.3} |
Guido van Rossum | 77f6a65 | 2002-04-03 22:41:51 +0000 | [diff] [blame] | 84 | \end{funcdesc} |
| 85 | |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 86 | \begin{funcdesc}{callable}{object} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 87 | Return true if the \var{object} argument appears callable, false if |
| 88 | not. If this returns true, it is still possible that a call fails, |
| 89 | but if it is false, calling \var{object} will never succeed. Note |
| 90 | that classes are callable (calling a class returns a new instance); |
| 91 | class instances are callable if they have a \method{__call__()} |
| 92 | method. |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 93 | \end{funcdesc} |
| 94 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 95 | \begin{funcdesc}{chr}{i} |
| 96 | Return a string of one character whose \ASCII{} code is the integer |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 97 | \var{i}. For example, \code{chr(97)} returns the string \code{'a'}. |
| 98 | This is the inverse of \function{ord()}. The argument must be in |
| 99 | the range [0..255], inclusive; \exception{ValueError} will be raised |
| 100 | if \var{i} is outside that range. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 101 | \end{funcdesc} |
| 102 | |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 103 | \begin{funcdesc}{classmethod}{function} |
| 104 | Return a class method for \var{function}. |
| 105 | |
| 106 | A class method receives the class as implicit first argument, |
| 107 | just like an instance method receives the instance. |
| 108 | To declare a class method, use this idiom: |
| 109 | |
| 110 | \begin{verbatim} |
| 111 | class C: |
| 112 | def f(cls, arg1, arg2, ...): ... |
| 113 | f = classmethod(f) |
| 114 | \end{verbatim} |
| 115 | |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 116 | It can be called either on the class (such as \code{C.f()}) or on an |
| 117 | instance (such as \code{C().f()}). The instance is ignored except for |
| 118 | its class. |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 119 | If a class method is called for a derived class, the derived class |
| 120 | object is passed as the implied first argument. |
| 121 | |
Fred Drake | 2884d6d | 2003-07-02 12:27:43 +0000 | [diff] [blame] | 122 | Class methods are different than \Cpp{} or Java static methods. |
Fred Drake | f91888b | 2003-06-26 03:11:57 +0000 | [diff] [blame] | 123 | If you want those, see \function{staticmethod()} in this section. |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 124 | \versionadded{2.2} |
| 125 | \end{funcdesc} |
| 126 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 127 | \begin{funcdesc}{cmp}{x, y} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 128 | Compare the two objects \var{x} and \var{y} and return an integer |
| 129 | according to the outcome. The return value is negative if \code{\var{x} |
| 130 | < \var{y}}, zero if \code{\var{x} == \var{y}} and strictly positive if |
| 131 | \code{\var{x} > \var{y}}. |
| 132 | \end{funcdesc} |
| 133 | |
Tim Peters | 32f453e | 2001-09-03 08:35:41 +0000 | [diff] [blame] | 134 | \begin{funcdesc}{compile}{string, filename, kind\optional{, |
Michael W. Hudson | 53da317 | 2001-08-27 20:02:17 +0000 | [diff] [blame] | 135 | flags\optional{, dont_inherit}}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 136 | Compile the \var{string} into a code object. Code objects can be |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 137 | executed by an \keyword{exec} statement or evaluated by a call to |
| 138 | \function{eval()}. The \var{filename} argument should |
Guido van Rossum | 0d68246 | 2001-09-29 14:28:52 +0000 | [diff] [blame] | 139 | give the file from which the code was read; pass some recognizable value |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 140 | if it wasn't read from a file (\code{'<string>'} is commonly used). |
| 141 | The \var{kind} argument specifies what kind of code must be |
| 142 | compiled; it can be \code{'exec'} if \var{string} consists of a |
| 143 | sequence of statements, \code{'eval'} if it consists of a single |
| 144 | expression, or \code{'single'} if it consists of a single |
| 145 | interactive statement (in the latter case, expression statements |
| 146 | that evaluate to something else than \code{None} will printed). |
Michael W. Hudson | 53da317 | 2001-08-27 20:02:17 +0000 | [diff] [blame] | 147 | |
Guido van Rossum | 0d68246 | 2001-09-29 14:28:52 +0000 | [diff] [blame] | 148 | When compiling multi-line statements, two caveats apply: line |
| 149 | endings must be represented by a single newline character |
| 150 | (\code{'\e n'}), and the input must be terminated by at least one |
| 151 | newline character. If line endings are represented by |
| 152 | \code{'\e r\e n'}, use the string \method{replace()} method to |
| 153 | change them into \code{'\e n'}. |
| 154 | |
| 155 | The optional arguments \var{flags} and \var{dont_inherit} |
Michael W. Hudson | 53da317 | 2001-08-27 20:02:17 +0000 | [diff] [blame] | 156 | (which are new in Python 2.2) control which future statements (see |
| 157 | \pep{236}) affect the compilation of \var{string}. If neither is |
| 158 | present (or both are zero) the code is compiled with those future |
| 159 | statements that are in effect in the code that is calling compile. |
| 160 | If the \var{flags} argument is given and \var{dont_inherit} is not |
| 161 | (or is zero) then the future statements specified by the \var{flags} |
| 162 | argument are used in addition to those that would be used anyway. |
| 163 | If \var{dont_inherit} is a non-zero integer then the \var{flags} |
| 164 | argument is it -- the future statements in effect around the call to |
| 165 | compile are ignored. |
| 166 | |
| 167 | Future statemants are specified by bits which can be bitwise or-ed |
| 168 | together to specify multiple statements. The bitfield required to |
| 169 | specify a given feature can be found as the \member{compiler_flag} |
| 170 | attribute on the \class{_Feature} instance in the |
| 171 | \module{__future__} module. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 172 | \end{funcdesc} |
| 173 | |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 174 | \begin{funcdesc}{complex}{\optional{real\optional{, imag}}} |
Guido van Rossum | cb1f242 | 1999-03-25 21:23:26 +0000 | [diff] [blame] | 175 | Create a complex number with the value \var{real} + \var{imag}*j or |
Fred Drake | 526c7a0 | 2001-12-13 19:52:22 +0000 | [diff] [blame] | 176 | convert a string or number to a complex number. If the first |
| 177 | parameter is a string, it will be interpreted as a complex number |
| 178 | and the function must be called without a second parameter. The |
| 179 | second parameter can never be a string. |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 180 | Each argument may be any numeric type (including complex). |
| 181 | If \var{imag} is omitted, it defaults to zero and the function |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 182 | serves as a numeric conversion function like \function{int()}, |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 183 | \function{long()} and \function{float()}. If both arguments |
| 184 | are omitted, returns \code{0j}. |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 185 | \end{funcdesc} |
| 186 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 187 | \begin{funcdesc}{delattr}{object, name} |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 188 | This is a relative of \function{setattr()}. The arguments are an |
Guido van Rossum | 1efbb0f | 1994-08-16 22:15:11 +0000 | [diff] [blame] | 189 | object and a string. The string must be the name |
| 190 | of one of the object's attributes. The function deletes |
| 191 | the named attribute, provided the object allows it. For example, |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 192 | \code{delattr(\var{x}, '\var{foobar}')} is equivalent to |
Guido van Rossum | 1efbb0f | 1994-08-16 22:15:11 +0000 | [diff] [blame] | 193 | \code{del \var{x}.\var{foobar}}. |
| 194 | \end{funcdesc} |
| 195 | |
Tim Peters | a427a2b | 2001-10-29 22:25:45 +0000 | [diff] [blame] | 196 | \begin{funcdesc}{dict}{\optional{mapping-or-sequence}} |
Just van Rossum | a797d81 | 2002-11-23 09:45:04 +0000 | [diff] [blame] | 197 | Return a new dictionary initialized from an optional positional |
| 198 | argument or from a set of keyword arguments. |
| 199 | If no arguments are given, return a new empty dictionary. |
| 200 | If the positional argument is a mapping object, return a dictionary |
| 201 | mapping the same keys to the same values as does the mapping object. |
| 202 | Otherwise the positional argument must be a sequence, a container that |
| 203 | supports iteration, or an iterator object. The elements of the argument |
| 204 | must each also be of one of those kinds, and each must in turn contain |
Tim Peters | 1fc240e | 2001-10-26 05:06:50 +0000 | [diff] [blame] | 205 | exactly two objects. The first is used as a key in the new dictionary, |
| 206 | and the second as the key's value. If a given key is seen more than |
| 207 | once, the last value associated with it is retained in the new |
| 208 | dictionary. |
Just van Rossum | a797d81 | 2002-11-23 09:45:04 +0000 | [diff] [blame] | 209 | |
| 210 | If keyword arguments are given, the keywords themselves with their |
| 211 | associated values are added as items to the dictionary. If a key |
| 212 | is specified both in the positional argument and as a keyword argument, |
| 213 | the value associated with the keyword is retained in the dictionary. |
Tim Peters | 1fc240e | 2001-10-26 05:06:50 +0000 | [diff] [blame] | 214 | For example, these all return a dictionary equal to |
Just van Rossum | a797d81 | 2002-11-23 09:45:04 +0000 | [diff] [blame] | 215 | \code{\{"one": 2, "two": 3\}}: |
Fred Drake | ef7d08a | 2001-10-26 15:04:33 +0000 | [diff] [blame] | 216 | |
| 217 | \begin{itemize} |
Just van Rossum | a797d81 | 2002-11-23 09:45:04 +0000 | [diff] [blame] | 218 | \item \code{dict(\{'one': 2, 'two': 3\})} |
| 219 | \item \code{dict(\{'one': 2, 'two': 3\}.items())} |
| 220 | \item \code{dict(\{'one': 2, 'two': 3\}.iteritems())} |
| 221 | \item \code{dict(zip(('one', 'two'), (2, 3)))} |
| 222 | \item \code{dict([['two', 3], ['one', 2]])} |
| 223 | \item \code{dict(one=2, two=3)} |
| 224 | \item \code{dict([(['one', 'two'][i-2], i) for i in (2, 3)])} |
Fred Drake | ef7d08a | 2001-10-26 15:04:33 +0000 | [diff] [blame] | 225 | \end{itemize} |
Fred Drake | da8a6dd | 2002-03-06 02:29:30 +0000 | [diff] [blame] | 226 | |
| 227 | \versionadded{2.2} |
Fred Drake | 6e596b6 | 2002-11-23 15:02:13 +0000 | [diff] [blame] | 228 | \versionchanged[Support for building a dictionary from keyword |
| 229 | arguments added]{2.3} |
Tim Peters | 1fc240e | 2001-10-26 05:06:50 +0000 | [diff] [blame] | 230 | \end{funcdesc} |
| 231 | |
Fred Drake | 6b303b4 | 1998-04-16 22:10:27 +0000 | [diff] [blame] | 232 | \begin{funcdesc}{dir}{\optional{object}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 233 | Without arguments, return the list of names in the current local |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 234 | symbol table. With an argument, attempts to return a list of valid |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 235 | attributes for that object. This information is gleaned from the |
Fred Drake | 3570551 | 2001-12-03 17:32:27 +0000 | [diff] [blame] | 236 | object's \member{__dict__} attribute, if defined, and from the class |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 237 | or type object. The list is not necessarily complete. |
| 238 | If the object is a module object, the list contains the names of the |
| 239 | module's attributes. |
| 240 | If the object is a type or class object, |
| 241 | the list contains the names of its attributes, |
| 242 | and recursively of the attributes of its bases. |
| 243 | Otherwise, the list contains the object's attributes' names, |
| 244 | the names of its class's attributes, |
| 245 | and recursively of the attributes of its class's base classes. |
| 246 | The resulting list is sorted alphabetically. |
| 247 | For example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 248 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 249 | \begin{verbatim} |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 250 | >>> import struct |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 251 | >>> dir() |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 252 | ['__builtins__', '__doc__', '__name__', 'struct'] |
| 253 | >>> dir(struct) |
| 254 | ['__doc__', '__name__', 'calcsize', 'error', 'pack', 'unpack'] |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 255 | \end{verbatim} |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 256 | |
| 257 | \note{Because \function{dir()} is supplied primarily as a convenience |
| 258 | for use at an interactive prompt, |
| 259 | it tries to supply an interesting set of names more than it tries to |
| 260 | supply a rigorously or consistently defined set of names, |
| 261 | and its detailed behavior may change across releases.} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 262 | \end{funcdesc} |
| 263 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 264 | \begin{funcdesc}{divmod}{a, b} |
Raymond Hettinger | 6cf09f0 | 2002-05-21 18:19:49 +0000 | [diff] [blame] | 265 | Take two (non complex) numbers as arguments and return a pair of numbers |
| 266 | consisting of their quotient and remainder when using long division. With |
| 267 | mixed operand types, the rules for binary arithmetic operators apply. For |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 268 | plain and long integers, the result is the same as |
| 269 | \code{(\var{a} / \var{b}, \var{a} \%{} \var{b})}. |
Fred Drake | 1ea7c75 | 1999-05-06 14:46:35 +0000 | [diff] [blame] | 270 | For floating point numbers the result is \code{(\var{q}, \var{a} \%{} |
| 271 | \var{b})}, where \var{q} is usually \code{math.floor(\var{a} / |
| 272 | \var{b})} but may be 1 less than that. In any case \code{\var{q} * |
| 273 | \var{b} + \var{a} \%{} \var{b}} is very close to \var{a}, if |
| 274 | \code{\var{a} \%{} \var{b}} is non-zero it has the same sign as |
| 275 | \var{b}, and \code{0 <= abs(\var{a} \%{} \var{b}) < abs(\var{b})}. |
Fred Drake | 807354f | 2002-06-20 21:10:25 +0000 | [diff] [blame] | 276 | |
| 277 | \versionchanged[Using \function{divmod()} with complex numbers is |
| 278 | deprecated]{2.3} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 279 | \end{funcdesc} |
| 280 | |
Fred Drake | 38f7197 | 2002-04-26 20:29:44 +0000 | [diff] [blame] | 281 | \begin{funcdesc}{enumerate}{iterable} |
| 282 | Return an enumerate object. \var{iterable} must be a sequence, an |
| 283 | iterator, or some other object which supports iteration. The |
| 284 | \method{next()} method of the iterator returned by |
| 285 | \function{enumerate()} returns a tuple containing a count (from |
| 286 | zero) and the corresponding value obtained from iterating over |
Fred Drake | 8f53cdc | 2003-05-10 19:46:39 +0000 | [diff] [blame] | 287 | \var{iterable}. \function{enumerate()} is useful for obtaining an |
Fred Drake | 38f7197 | 2002-04-26 20:29:44 +0000 | [diff] [blame] | 288 | indexed series: \code{(0, seq[0])}, \code{(1, seq[1])}, \code{(2, |
| 289 | seq[2])}, \ldots. |
| 290 | \versionadded{2.3} |
| 291 | \end{funcdesc} |
| 292 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 293 | \begin{funcdesc}{eval}{expression\optional{, globals\optional{, locals}}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 294 | The arguments are a string and two optional dictionaries. The |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 295 | \var{expression} argument is parsed and evaluated as a Python |
| 296 | expression (technically speaking, a condition list) using the |
| 297 | \var{globals} and \var{locals} dictionaries as global and local name |
Neal Norwitz | 046b8a7 | 2002-12-17 01:08:06 +0000 | [diff] [blame] | 298 | space. If the \var{globals} dictionary is present and lacks |
| 299 | '__builtins__', the current globals are copied into \var{globals} before |
| 300 | \var{expression} is parsed. This means that \var{expression} |
| 301 | normally has full access to the standard |
| 302 | \refmodule[builtin]{__builtin__} module and restricted environments |
| 303 | are propagated. If the \var{locals} dictionary is omitted it defaults to |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 304 | the \var{globals} dictionary. If both dictionaries are omitted, the |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 305 | expression is executed in the environment where \keyword{eval} is |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 306 | called. The return value is the result of the evaluated expression. |
| 307 | Syntax errors are reported as exceptions. Example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 308 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 309 | \begin{verbatim} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 310 | >>> x = 1 |
| 311 | >>> print eval('x+1') |
| 312 | 2 |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 313 | \end{verbatim} |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 314 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 315 | This function can also be used to execute arbitrary code objects |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 316 | (such as those created by \function{compile()}). In this case pass |
| 317 | a code object instead of a string. The code object must have been |
| 318 | compiled passing \code{'eval'} as the \var{kind} argument. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 319 | |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 320 | Hints: dynamic execution of statements is supported by the |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 321 | \keyword{exec} statement. Execution of statements from a file is |
| 322 | supported by the \function{execfile()} function. The |
| 323 | \function{globals()} and \function{locals()} functions returns the |
| 324 | current global and local dictionary, respectively, which may be |
| 325 | useful to pass around for use by \function{eval()} or |
| 326 | \function{execfile()}. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 327 | \end{funcdesc} |
| 328 | |
Raymond Hettinger | 774816f | 2003-07-02 15:31:54 +0000 | [diff] [blame] | 329 | \begin{funcdesc}{execfile}{filename\optional{, globals\optional{, locals}}} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 330 | This function is similar to the |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 331 | \keyword{exec} statement, but parses a file instead of a string. It |
| 332 | is different from the \keyword{import} statement in that it does not |
| 333 | use the module administration --- it reads the file unconditionally |
| 334 | and does not create a new module.\footnote{It is used relatively |
| 335 | rarely so does not warrant being made into a statement.} |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 336 | |
| 337 | The arguments are a file name and two optional dictionaries. The |
| 338 | file is parsed and evaluated as a sequence of Python statements |
| 339 | (similarly to a module) using the \var{globals} and \var{locals} |
Fred Drake | 1349437 | 2000-09-12 16:23:48 +0000 | [diff] [blame] | 340 | dictionaries as global and local namespace. If the \var{locals} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 341 | dictionary is omitted it defaults to the \var{globals} dictionary. |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 342 | If both dictionaries are omitted, the expression is executed in the |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 343 | environment where \function{execfile()} is called. The return value is |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 344 | \code{None}. |
Tim Peters | af5910f | 2001-09-30 06:32:59 +0000 | [diff] [blame] | 345 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 346 | \warning{The default \var{locals} act as described for function |
Tim Peters | af5910f | 2001-09-30 06:32:59 +0000 | [diff] [blame] | 347 | \function{locals()} below: modifications to the default \var{locals} |
| 348 | dictionary should not be attempted. Pass an explicit \var{locals} |
| 349 | dictionary if you need to see effects of the code on \var{locals} after |
| 350 | function \function{execfile()} returns. \function{execfile()} cannot |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 351 | be used reliably to modify a function's locals.} |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 352 | \end{funcdesc} |
| 353 | |
Tim Peters | 2e29bfb | 2001-09-20 19:55:29 +0000 | [diff] [blame] | 354 | \begin{funcdesc}{file}{filename\optional{, mode\optional{, bufsize}}} |
| 355 | Return a new file object (described earlier under Built-in Types). |
| 356 | The first two arguments are the same as for \code{stdio}'s |
| 357 | \cfunction{fopen()}: \var{filename} is the file name to be opened, |
| 358 | \var{mode} indicates how the file is to be opened: \code{'r'} for |
| 359 | reading, \code{'w'} for writing (truncating an existing file), and |
| 360 | \code{'a'} opens it for appending (which on \emph{some} \UNIX{} |
| 361 | systems means that \emph{all} writes append to the end of the file, |
| 362 | regardless of the current seek position). |
| 363 | |
| 364 | Modes \code{'r+'}, \code{'w+'} and \code{'a+'} open the file for |
| 365 | updating (note that \code{'w+'} truncates the file). Append |
| 366 | \code{'b'} to the mode to open the file in binary mode, on systems |
| 367 | that differentiate between binary and text files (else it is |
| 368 | ignored). If the file cannot be opened, \exception{IOError} is |
| 369 | raised. |
Barry Warsaw | 177b4a0 | 2002-05-22 20:39:43 +0000 | [diff] [blame] | 370 | |
| 371 | In addition to the standard \cfunction{fopen()} values \var{mode} |
| 372 | may be \code{'U'} or \code{'rU'}. If Python is built with universal |
| 373 | newline support (the default) the file is opened as a text file, but |
| 374 | lines may be terminated by any of \code{'\e n'}, the Unix end-of-line |
| 375 | convention, |
| 376 | \code{'\e r'}, the Macintosh convention or \code{'\e r\e n'}, the Windows |
| 377 | convention. All of these external representations are seen as |
| 378 | \code{'\e n'} |
| 379 | by the Python program. If Python is built without universal newline support |
| 380 | \var{mode} \code{'U'} is the same as normal text mode. Note that |
| 381 | file objects so opened also have an attribute called |
| 382 | \member{newlines} which has a value of \code{None} (if no newlines |
| 383 | have yet been seen), \code{'\e n'}, \code{'\e r'}, \code{'\e r\e n'}, |
| 384 | or a tuple containing all the newline types seen. |
Tim Peters | 2e29bfb | 2001-09-20 19:55:29 +0000 | [diff] [blame] | 385 | |
| 386 | If \var{mode} is omitted, it defaults to \code{'r'}. When opening a |
| 387 | binary file, you should append \code{'b'} to the \var{mode} value |
| 388 | for improved portability. (It's useful even on systems which don't |
| 389 | treat binary and text files differently, where it serves as |
| 390 | documentation.) |
| 391 | \index{line-buffered I/O}\index{unbuffered I/O}\index{buffer size, I/O} |
| 392 | \index{I/O control!buffering} |
| 393 | The optional \var{bufsize} argument specifies the |
| 394 | file's desired buffer size: 0 means unbuffered, 1 means line |
| 395 | buffered, any other positive value means use a buffer of |
| 396 | (approximately) that size. A negative \var{bufsize} means to use |
Raymond Hettinger | 999b57c | 2003-08-25 04:28:05 +0000 | [diff] [blame] | 397 | the system default, which is usually line buffered for tty |
Tim Peters | 2e29bfb | 2001-09-20 19:55:29 +0000 | [diff] [blame] | 398 | devices and fully buffered for other files. If omitted, the system |
| 399 | default is used.\footnote{ |
| 400 | Specifying a buffer size currently has no effect on systems that |
| 401 | don't have \cfunction{setvbuf()}. The interface to specify the |
| 402 | buffer size is not done using a method that calls |
| 403 | \cfunction{setvbuf()}, because that may dump core when called |
| 404 | after any I/O has been performed, and there's no reliable way to |
| 405 | determine whether this is the case.} |
| 406 | |
| 407 | The \function{file()} constructor is new in Python 2.2. The previous |
| 408 | spelling, \function{open()}, is retained for compatibility, and is an |
| 409 | alias for \function{file()}. |
| 410 | \end{funcdesc} |
| 411 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 412 | \begin{funcdesc}{filter}{function, list} |
Fred Drake | eacdec6 | 2001-05-02 20:19:19 +0000 | [diff] [blame] | 413 | Construct a list from those elements of \var{list} for which |
| 414 | \var{function} returns true. \var{list} may be either a sequence, a |
| 415 | container which supports iteration, or an iterator, If \var{list} |
| 416 | is a string or a tuple, the result also has that type; otherwise it |
| 417 | is always a list. If \var{function} is \code{None}, the identity |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 418 | function is assumed, that is, all elements of \var{list} that are false |
Fred Drake | eacdec6 | 2001-05-02 20:19:19 +0000 | [diff] [blame] | 419 | (zero or empty) are removed. |
Martin v. Löwis | 7472336 | 2003-05-31 08:02:38 +0000 | [diff] [blame] | 420 | |
Fred Drake | 2884d6d | 2003-07-02 12:27:43 +0000 | [diff] [blame] | 421 | Note that \code{filter(function, \var{list})} is equivalent to |
| 422 | \code{[item for item in \var{list} if function(item)]} if function is |
| 423 | not \code{None} and \code{[item for item in \var{list} if item]} if |
| 424 | function is \code{None}. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 425 | \end{funcdesc} |
| 426 | |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 427 | \begin{funcdesc}{float}{\optional{x}} |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 428 | Convert a string or a number to floating point. If the argument is a |
Fred Drake | d83675f | 1998-12-07 17:13:18 +0000 | [diff] [blame] | 429 | string, it must contain a possibly signed decimal or floating point |
Fred Drake | 70a66c9 | 1999-02-18 16:08:36 +0000 | [diff] [blame] | 430 | number, possibly embedded in whitespace; this behaves identical to |
| 431 | \code{string.atof(\var{x})}. Otherwise, the argument may be a plain |
| 432 | or long integer or a floating point number, and a floating point |
| 433 | number with the same value (within Python's floating point |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 434 | precision) is returned. If no argument is given, returns \code{0.0}. |
Fred Drake | 70a66c9 | 1999-02-18 16:08:36 +0000 | [diff] [blame] | 435 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 436 | \note{When passing in a string, values for NaN\index{NaN} |
Fred Drake | 70a66c9 | 1999-02-18 16:08:36 +0000 | [diff] [blame] | 437 | and Infinity\index{Infinity} may be returned, depending on the |
| 438 | underlying C library. The specific set of strings accepted which |
| 439 | cause these values to be returned depends entirely on the C library |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 440 | and is known to vary.} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 441 | \end{funcdesc} |
| 442 | |
Raymond Hettinger | a690a99 | 2003-11-16 16:17:49 +0000 | [diff] [blame] | 443 | \begin{funcdesc}{frozenset}{\optional{iterable}} |
| 444 | Return a frozenset object whose elements are taken from \var{iterable}. |
| 445 | Frozensets are sets that have no update methods but can be hashed and |
| 446 | used as members of other sets or as dictionary keys. The elements of |
| 447 | a frozenset must be immutable themselves. To represent sets of sets, |
| 448 | the inner sets should also be \class{frozenset} objects. If |
| 449 | \var{iterable} is not specified, returns a new empty set, |
| 450 | \code{frozenset([])}. |
| 451 | \versionadded{2.4} |
| 452 | \end{funcdesc} |
| 453 | |
Fred Drake | de5d5ce | 1999-07-22 19:21:45 +0000 | [diff] [blame] | 454 | \begin{funcdesc}{getattr}{object, name\optional{, default}} |
| 455 | Return the value of the named attributed of \var{object}. \var{name} |
| 456 | must be a string. If the string is the name of one of the object's |
| 457 | attributes, the result is the value of that attribute. For example, |
| 458 | \code{getattr(x, 'foobar')} is equivalent to \code{x.foobar}. If the |
| 459 | named attribute does not exist, \var{default} is returned if provided, |
| 460 | otherwise \exception{AttributeError} is raised. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 461 | \end{funcdesc} |
| 462 | |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 463 | \begin{funcdesc}{globals}{} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 464 | Return a dictionary representing the current global symbol table. |
| 465 | This is always the dictionary of the current module (inside a |
| 466 | function or method, this is the module where it is defined, not the |
| 467 | module from which it is called). |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 468 | \end{funcdesc} |
| 469 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 470 | \begin{funcdesc}{hasattr}{object, name} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 471 | The arguments are an object and a string. The result is 1 if the |
| 472 | string is the name of one of the object's attributes, 0 if not. |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 473 | (This is implemented by calling \code{getattr(\var{object}, |
| 474 | \var{name})} and seeing whether it raises an exception or not.) |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 475 | \end{funcdesc} |
| 476 | |
| 477 | \begin{funcdesc}{hash}{object} |
| 478 | Return the hash value of the object (if it has one). Hash values |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 479 | are integers. They are used to quickly compare dictionary |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 480 | keys during a dictionary lookup. Numeric values that compare equal |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 481 | have the same hash value (even if they are of different types, as is |
| 482 | the case for 1 and 1.0). |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 483 | \end{funcdesc} |
| 484 | |
Fred Drake | 732299f | 2001-12-18 16:31:08 +0000 | [diff] [blame] | 485 | \begin{funcdesc}{help}{\optional{object}} |
| 486 | Invoke the built-in help system. (This function is intended for |
| 487 | interactive use.) If no argument is given, the interactive help |
| 488 | system starts on the interpreter console. If the argument is a |
| 489 | string, then the string is looked up as the name of a module, |
| 490 | function, class, method, keyword, or documentation topic, and a |
| 491 | help page is printed on the console. If the argument is any other |
| 492 | kind of object, a help page on the object is generated. |
Fred Drake | 933f159 | 2002-04-17 12:54:04 +0000 | [diff] [blame] | 493 | \versionadded{2.2} |
Fred Drake | 732299f | 2001-12-18 16:31:08 +0000 | [diff] [blame] | 494 | \end{funcdesc} |
| 495 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 496 | \begin{funcdesc}{hex}{x} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 497 | Convert an integer number (of any size) to a hexadecimal string. |
Guido van Rossum | 5cd7520 | 1997-01-14 18:44:23 +0000 | [diff] [blame] | 498 | The result is a valid Python expression. Note: this always yields |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 499 | an unsigned literal. For example, on a 32-bit machine, |
| 500 | \code{hex(-1)} yields \code{'0xffffffff'}. When evaluated on a |
| 501 | machine with the same word size, this literal is evaluated as -1; at |
| 502 | a different word size, it may turn up as a large positive number or |
| 503 | raise an \exception{OverflowError} exception. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 504 | \end{funcdesc} |
| 505 | |
| 506 | \begin{funcdesc}{id}{object} |
Fred Drake | 8aa3bd9 | 2000-06-29 03:46:46 +0000 | [diff] [blame] | 507 | Return the `identity' of an object. This is an integer (or long |
| 508 | integer) which is guaranteed to be unique and constant for this |
| 509 | object during its lifetime. Two objects whose lifetimes are |
| 510 | disjunct may have the same \function{id()} value. (Implementation |
| 511 | note: this is the address of the object.) |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 512 | \end{funcdesc} |
| 513 | |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 514 | \begin{funcdesc}{input}{\optional{prompt}} |
Guido van Rossum | 777dcc6 | 1998-06-17 15:16:40 +0000 | [diff] [blame] | 515 | Equivalent to \code{eval(raw_input(\var{prompt}))}. |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 516 | \warning{This function is not safe from user errors! It |
Fred Drake | f96e0d2 | 2000-09-09 03:33:42 +0000 | [diff] [blame] | 517 | expects a valid Python expression as input; if the input is not |
| 518 | syntactically valid, a \exception{SyntaxError} will be raised. |
| 519 | Other exceptions may be raised if there is an error during |
| 520 | evaluation. (On the other hand, sometimes this is exactly what you |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 521 | need when writing a quick script for expert use.)} |
Fred Drake | f96e0d2 | 2000-09-09 03:33:42 +0000 | [diff] [blame] | 522 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 523 | If the \refmodule{readline} module was loaded, then |
Fred Drake | f96e0d2 | 2000-09-09 03:33:42 +0000 | [diff] [blame] | 524 | \function{input()} will use it to provide elaborate line editing and |
| 525 | history features. |
| 526 | |
| 527 | Consider using the \function{raw_input()} function for general input |
| 528 | from users. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 529 | \end{funcdesc} |
| 530 | |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 531 | \begin{funcdesc}{int}{\optional{x\optional{, radix}}} |
Fred Drake | 1e862e8 | 2000-02-17 17:45:52 +0000 | [diff] [blame] | 532 | Convert a string or number to a plain integer. If the argument is a |
| 533 | string, it must contain a possibly signed decimal number |
Martin v. Löwis | 7472336 | 2003-05-31 08:02:38 +0000 | [diff] [blame] | 534 | representable as a Python integer, possibly embedded in whitespace. |
| 535 | The \var{radix} parameter gives the base for the |
Fred Drake | 17383b9 | 2000-11-17 19:44:14 +0000 | [diff] [blame] | 536 | conversion and may be any integer in the range [2, 36], or zero. If |
| 537 | \var{radix} is zero, the proper radix is guessed based on the |
| 538 | contents of string; the interpretation is the same as for integer |
| 539 | literals. If \var{radix} is specified and \var{x} is not a string, |
Fred Drake | 1e862e8 | 2000-02-17 17:45:52 +0000 | [diff] [blame] | 540 | \exception{TypeError} is raised. |
| 541 | Otherwise, the argument may be a plain or |
| 542 | long integer or a floating point number. Conversion of floating |
Tim Peters | 7321ec4 | 2001-07-26 20:02:17 +0000 | [diff] [blame] | 543 | point numbers to integers truncates (towards zero). |
Walter Dörwald | f171540 | 2002-11-19 20:49:15 +0000 | [diff] [blame] | 544 | If the argument is outside the integer range a long object will |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 545 | be returned instead. If no arguments are given, returns \code{0}. |
Fred Drake | 1e862e8 | 2000-02-17 17:45:52 +0000 | [diff] [blame] | 546 | \end{funcdesc} |
| 547 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 548 | \begin{funcdesc}{isinstance}{object, classinfo} |
| 549 | Return true if the \var{object} argument is an instance of the |
| 550 | \var{classinfo} argument, or of a (direct or indirect) subclass |
| 551 | thereof. Also return true if \var{classinfo} is a type object and |
| 552 | \var{object} is an object of that type. If \var{object} is not a |
Walter Dörwald | 2e0b18a | 2003-01-31 17:19:08 +0000 | [diff] [blame] | 553 | class instance or an object of the given type, the function always |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 554 | returns false. If \var{classinfo} is neither a class object nor a |
| 555 | type object, it may be a tuple of class or type objects, or may |
| 556 | recursively contain other such tuples (other sequence types are not |
| 557 | accepted). If \var{classinfo} is not a class, type, or tuple of |
| 558 | classes, types, and such tuples, a \exception{TypeError} exception |
| 559 | is raised. |
| 560 | \versionchanged[Support for a tuple of type information was added]{2.2} |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 561 | \end{funcdesc} |
| 562 | |
Walter Dörwald | d9a6ad3 | 2002-12-12 16:41:44 +0000 | [diff] [blame] | 563 | \begin{funcdesc}{issubclass}{class, classinfo} |
| 564 | Return true if \var{class} is a subclass (direct or indirect) of |
| 565 | \var{classinfo}. A class is considered a subclass of itself. |
| 566 | \var{classinfo} may be a tuple of class objects, in which case every |
| 567 | entry in \var{classinfo} will be checked. In any other case, a |
| 568 | \exception{TypeError} exception is raised. |
| 569 | \versionchanged[Support for a tuple of type information was added]{2.3} |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 570 | \end{funcdesc} |
| 571 | |
Fred Drake | 00bb329 | 2001-09-06 19:04:29 +0000 | [diff] [blame] | 572 | \begin{funcdesc}{iter}{o\optional{, sentinel}} |
| 573 | Return an iterator object. The first argument is interpreted very |
| 574 | differently depending on the presence of the second argument. |
| 575 | Without a second argument, \var{o} must be a collection object which |
| 576 | supports the iteration protocol (the \method{__iter__()} method), or |
| 577 | it must support the sequence protocol (the \method{__getitem__()} |
| 578 | method with integer arguments starting at \code{0}). If it does not |
| 579 | support either of those protocols, \exception{TypeError} is raised. |
| 580 | If the second argument, \var{sentinel}, is given, then \var{o} must |
| 581 | be a callable object. The iterator created in this case will call |
| 582 | \var{o} with no arguments for each call to its \method{next()} |
| 583 | method; if the value returned is equal to \var{sentinel}, |
| 584 | \exception{StopIteration} will be raised, otherwise the value will |
| 585 | be returned. |
| 586 | \versionadded{2.2} |
| 587 | \end{funcdesc} |
| 588 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 589 | \begin{funcdesc}{len}{s} |
| 590 | Return the length (the number of items) of an object. The argument |
| 591 | may be a sequence (string, tuple or list) or a mapping (dictionary). |
| 592 | \end{funcdesc} |
| 593 | |
Tim Peters | 1fc240e | 2001-10-26 05:06:50 +0000 | [diff] [blame] | 594 | \begin{funcdesc}{list}{\optional{sequence}} |
Fred Drake | eacdec6 | 2001-05-02 20:19:19 +0000 | [diff] [blame] | 595 | Return a list whose items are the same and in the same order as |
| 596 | \var{sequence}'s items. \var{sequence} may be either a sequence, a |
| 597 | container that supports iteration, or an iterator object. If |
| 598 | \var{sequence} is already a list, a copy is made and returned, |
| 599 | similar to \code{\var{sequence}[:]}. For instance, |
| 600 | \code{list('abc')} returns \code{['a', 'b', 'c']} and \code{list( |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 601 | (1, 2, 3) )} returns \code{[1, 2, 3]}. If no argument is given, |
| 602 | returns a new empty list, \code{[]}. |
Guido van Rossum | 921f32c | 1997-06-02 17:21:20 +0000 | [diff] [blame] | 603 | \end{funcdesc} |
| 604 | |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 605 | \begin{funcdesc}{locals}{} |
Raymond Hettinger | 69bf8f3 | 2003-01-04 02:16:22 +0000 | [diff] [blame] | 606 | Update and return a dictionary representing the current local symbol table. |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 607 | \warning{The contents of this dictionary should not be modified; |
| 608 | changes may not affect the values of local variables used by the |
| 609 | interpreter.} |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 610 | \end{funcdesc} |
| 611 | |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 612 | \begin{funcdesc}{long}{\optional{x\optional{, radix}}} |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 613 | Convert a string or number to a long integer. If the argument is a |
Fred Drake | 9c15fa7 | 2001-01-04 05:09:16 +0000 | [diff] [blame] | 614 | string, it must contain a possibly signed number of |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 615 | arbitrary size, possibly embedded in whitespace; |
Fred Drake | 17383b9 | 2000-11-17 19:44:14 +0000 | [diff] [blame] | 616 | this behaves identical to \code{string.atol(\var{x})}. The |
| 617 | \var{radix} argument is interpreted in the same way as for |
| 618 | \function{int()}, and may only be given when \var{x} is a string. |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 619 | Otherwise, the argument may be a plain or |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 620 | long integer or a floating point number, and a long integer with |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 621 | the same value is returned. Conversion of floating |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 622 | point numbers to integers truncates (towards zero). If no arguments |
| 623 | are given, returns \code{0L}. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 624 | \end{funcdesc} |
| 625 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 626 | \begin{funcdesc}{map}{function, list, ...} |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 627 | Apply \var{function} to every item of \var{list} and return a list |
| 628 | of the results. If additional \var{list} arguments are passed, |
| 629 | \var{function} must take that many arguments and is applied to the |
| 630 | items of all lists in parallel; if a list is shorter than another it |
| 631 | is assumed to be extended with \code{None} items. If \var{function} |
| 632 | is \code{None}, the identity function is assumed; if there are |
| 633 | multiple list arguments, \function{map()} returns a list consisting |
| 634 | of tuples containing the corresponding items from all lists (a kind |
| 635 | of transpose operation). The \var{list} arguments may be any kind |
| 636 | of sequence; the result is always a list. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 637 | \end{funcdesc} |
| 638 | |
Guido van Rossum | 5eabf38 | 1998-11-25 18:53:05 +0000 | [diff] [blame] | 639 | \begin{funcdesc}{max}{s\optional{, args...}} |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 640 | With a single argument \var{s}, return the largest item of a |
| 641 | non-empty sequence (such as a string, tuple or list). With more |
| 642 | than one argument, return the largest of the arguments. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 643 | \end{funcdesc} |
| 644 | |
Guido van Rossum | 5eabf38 | 1998-11-25 18:53:05 +0000 | [diff] [blame] | 645 | \begin{funcdesc}{min}{s\optional{, args...}} |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 646 | With a single argument \var{s}, return the smallest item of a |
| 647 | non-empty sequence (such as a string, tuple or list). With more |
| 648 | than one argument, return the smallest of the arguments. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 649 | \end{funcdesc} |
| 650 | |
Raymond Hettinger | 7e902b2 | 2003-06-11 09:15:26 +0000 | [diff] [blame] | 651 | \begin{funcdesc}{object}{} |
Fred Drake | f91888b | 2003-06-26 03:11:57 +0000 | [diff] [blame] | 652 | Return a new featureless object. \function{object()} is a base |
| 653 | for all new style classes. It has the methods that are common |
| 654 | to all instances of new style classes. |
| 655 | \versionadded{2.2} |
Raymond Hettinger | 7e902b2 | 2003-06-11 09:15:26 +0000 | [diff] [blame] | 656 | |
Fred Drake | f91888b | 2003-06-26 03:11:57 +0000 | [diff] [blame] | 657 | \versionchanged[This function does not accept any arguments. |
| 658 | Formerly, it accepted arguments but ignored them]{2.3} |
Raymond Hettinger | 7e902b2 | 2003-06-11 09:15:26 +0000 | [diff] [blame] | 659 | \end{funcdesc} |
| 660 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 661 | \begin{funcdesc}{oct}{x} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 662 | Convert an integer number (of any size) to an octal string. The |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 663 | result is a valid Python expression. Note: this always yields an |
| 664 | unsigned literal. For example, on a 32-bit machine, \code{oct(-1)} |
| 665 | yields \code{'037777777777'}. When evaluated on a machine with the |
| 666 | same word size, this literal is evaluated as -1; at a different word |
Guido van Rossum | 5cd7520 | 1997-01-14 18:44:23 +0000 | [diff] [blame] | 667 | size, it may turn up as a large positive number or raise an |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 668 | \exception{OverflowError} exception. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 669 | \end{funcdesc} |
| 670 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 671 | \begin{funcdesc}{open}{filename\optional{, mode\optional{, bufsize}}} |
Tim Peters | 2e29bfb | 2001-09-20 19:55:29 +0000 | [diff] [blame] | 672 | An alias for the \function{file()} function above. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 673 | \end{funcdesc} |
| 674 | |
| 675 | \begin{funcdesc}{ord}{c} |
Fred Drake | 33d5184 | 2000-04-06 14:43:12 +0000 | [diff] [blame] | 676 | Return the \ASCII{} value of a string of one character or a Unicode |
| 677 | character. E.g., \code{ord('a')} returns the integer \code{97}, |
Raymond Hettinger | 9981213 | 2003-09-06 05:47:31 +0000 | [diff] [blame] | 678 | \code{ord(u'\e u2020')} returns \code{8224}. This is the inverse of |
Fred Drake | 33d5184 | 2000-04-06 14:43:12 +0000 | [diff] [blame] | 679 | \function{chr()} for strings and of \function{unichr()} for Unicode |
| 680 | characters. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 681 | \end{funcdesc} |
| 682 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 683 | \begin{funcdesc}{pow}{x, y\optional{, z}} |
Guido van Rossum | b8b264b | 1994-08-12 13:13:50 +0000 | [diff] [blame] | 684 | Return \var{x} to the power \var{y}; if \var{z} is present, return |
| 685 | \var{x} to the power \var{y}, modulo \var{z} (computed more |
Guido van Rossum | bf5a774 | 2001-07-12 11:27:16 +0000 | [diff] [blame] | 686 | efficiently than \code{pow(\var{x}, \var{y}) \%\ \var{z}}). The |
| 687 | arguments must have numeric types. With mixed operand types, the |
| 688 | coercion rules for binary arithmetic operators apply. For int and |
| 689 | long int operands, the result has the same type as the operands |
| 690 | (after coercion) unless the second argument is negative; in that |
| 691 | case, all arguments are converted to float and a float result is |
| 692 | delivered. For example, \code{10**2} returns \code{100}, but |
| 693 | \code{10**-2} returns \code{0.01}. (This last feature was added in |
Tim Peters | 32f453e | 2001-09-03 08:35:41 +0000 | [diff] [blame] | 694 | Python 2.2. In Python 2.1 and before, if both arguments were of integer |
| 695 | types and the second argument was negative, an exception was raised.) |
Tim Peters | 2e29bfb | 2001-09-20 19:55:29 +0000 | [diff] [blame] | 696 | If the second argument is negative, the third argument must be omitted. |
Tim Peters | 32f453e | 2001-09-03 08:35:41 +0000 | [diff] [blame] | 697 | If \var{z} is present, \var{x} and \var{y} must be of integer types, |
| 698 | and \var{y} must be non-negative. (This restriction was added in |
| 699 | Python 2.2. In Python 2.1 and before, floating 3-argument \code{pow()} |
| 700 | returned platform-dependent results depending on floating-point |
| 701 | rounding accidents.) |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 702 | \end{funcdesc} |
| 703 | |
Fred Drake | 8f53cdc | 2003-05-10 19:46:39 +0000 | [diff] [blame] | 704 | \begin{funcdesc}{property}{\optional{fget\optional{, fset\optional{, |
| 705 | fdel\optional{, doc}}}}} |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 706 | Return a property attribute for new-style classes (classes that |
Fred Drake | 8f53cdc | 2003-05-10 19:46:39 +0000 | [diff] [blame] | 707 | derive from \class{object}). |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 708 | |
| 709 | \var{fget} is a function for getting an attribute value, likewise |
| 710 | \var{fset} is a function for setting, and \var{fdel} a function |
| 711 | for del'ing, an attribute. Typical use is to define a managed attribute x: |
| 712 | |
| 713 | \begin{verbatim} |
| 714 | class C(object): |
| 715 | def getx(self): return self.__x |
| 716 | def setx(self, value): self.__x = value |
| 717 | def delx(self): del self.__x |
Neal Norwitz | b25229d | 2003-07-05 17:37:58 +0000 | [diff] [blame] | 718 | x = property(getx, setx, delx, "I'm the 'x' property.") |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 719 | \end{verbatim} |
| 720 | |
| 721 | \versionadded{2.2} |
| 722 | \end{funcdesc} |
| 723 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 724 | \begin{funcdesc}{range}{\optional{start,} stop\optional{, step}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 725 | This is a versatile function to create lists containing arithmetic |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 726 | progressions. It is most often used in \keyword{for} loops. The |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 727 | arguments must be plain integers. If the \var{step} argument is |
| 728 | omitted, it defaults to \code{1}. If the \var{start} argument is |
| 729 | omitted, it defaults to \code{0}. The full form returns a list of |
| 730 | plain integers \code{[\var{start}, \var{start} + \var{step}, |
| 731 | \var{start} + 2 * \var{step}, \ldots]}. If \var{step} is positive, |
| 732 | the last element is the largest \code{\var{start} + \var{i} * |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 733 | \var{step}} less than \var{stop}; if \var{step} is negative, the last |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 734 | element is the largest \code{\var{start} + \var{i} * \var{step}} |
Fred Drake | 6251c16 | 1998-04-03 07:15:54 +0000 | [diff] [blame] | 735 | greater than \var{stop}. \var{step} must not be zero (or else |
| 736 | \exception{ValueError} is raised). Example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 737 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 738 | \begin{verbatim} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 739 | >>> range(10) |
| 740 | [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] |
| 741 | >>> range(1, 11) |
| 742 | [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] |
| 743 | >>> range(0, 30, 5) |
| 744 | [0, 5, 10, 15, 20, 25] |
| 745 | >>> range(0, 10, 3) |
| 746 | [0, 3, 6, 9] |
| 747 | >>> range(0, -10, -1) |
| 748 | [0, -1, -2, -3, -4, -5, -6, -7, -8, -9] |
| 749 | >>> range(0) |
| 750 | [] |
| 751 | >>> range(1, 0) |
| 752 | [] |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 753 | \end{verbatim} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 754 | \end{funcdesc} |
| 755 | |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 756 | \begin{funcdesc}{raw_input}{\optional{prompt}} |
| 757 | If the \var{prompt} argument is present, it is written to standard output |
| 758 | without a trailing newline. The function then reads a line from input, |
| 759 | converts it to a string (stripping a trailing newline), and returns that. |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 760 | When \EOF{} is read, \exception{EOFError} is raised. Example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 761 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 762 | \begin{verbatim} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 763 | >>> s = raw_input('--> ') |
| 764 | --> Monty Python's Flying Circus |
| 765 | >>> s |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 766 | "Monty Python's Flying Circus" |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 767 | \end{verbatim} |
Guido van Rossum | 921f32c | 1997-06-02 17:21:20 +0000 | [diff] [blame] | 768 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 769 | If the \refmodule{readline} module was loaded, then |
| 770 | \function{raw_input()} will use it to provide elaborate |
| 771 | line editing and history features. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 772 | \end{funcdesc} |
| 773 | |
Guido van Rossum | 87e611e | 1999-01-06 23:10:51 +0000 | [diff] [blame] | 774 | \begin{funcdesc}{reduce}{function, sequence\optional{, initializer}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 775 | Apply \var{function} of two arguments cumulatively to the items of |
| 776 | \var{sequence}, from left to right, so as to reduce the sequence to |
Fred Drake | 2095b96 | 2002-07-17 13:55:33 +0000 | [diff] [blame] | 777 | a single value. For example, \code{reduce(lambda x, y: x+y, [1, 2, |
Raymond Hettinger | c2a2832 | 2003-10-13 17:52:35 +0000 | [diff] [blame] | 778 | 3, 4, 5])} calculates \code{((((1+2)+3)+4)+5)}. The left argument, |
| 779 | \var{x}, is the accumulated value and the right argument, \var{y}, |
| 780 | is the update value from the \var{sequence}. If the optional |
Fred Drake | 2095b96 | 2002-07-17 13:55:33 +0000 | [diff] [blame] | 781 | \var{initializer} is present, it is placed before the items of the |
| 782 | sequence in the calculation, and serves as a default when the |
| 783 | sequence is empty. If \var{initializer} is not given and |
| 784 | \var{sequence} contains only one item, the first item is returned. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 785 | \end{funcdesc} |
| 786 | |
| 787 | \begin{funcdesc}{reload}{module} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 788 | Re-parse and re-initialize an already imported \var{module}. The |
| 789 | argument must be a module object, so it must have been successfully |
| 790 | imported before. This is useful if you have edited the module |
| 791 | source file using an external editor and want to try out the new |
| 792 | version without leaving the Python interpreter. The return value is |
| 793 | the module object (the same as the \var{module} argument). |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 794 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 795 | There are a number of caveats: |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 796 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 797 | If a module is syntactically correct but its initialization fails, |
| 798 | the first \keyword{import} statement for it does not bind its name |
| 799 | locally, but does store a (partially initialized) module object in |
| 800 | \code{sys.modules}. To reload the module you must first |
| 801 | \keyword{import} it again (this will bind the name to the partially |
| 802 | initialized module object) before you can \function{reload()} it. |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 803 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 804 | When a module is reloaded, its dictionary (containing the module's |
| 805 | global variables) is retained. Redefinitions of names will override |
| 806 | the old definitions, so this is generally not a problem. If the new |
| 807 | version of a module does not define a name that was defined by the |
| 808 | old version, the old definition remains. This feature can be used |
| 809 | to the module's advantage if it maintains a global table or cache of |
| 810 | objects --- with a \keyword{try} statement it can test for the |
| 811 | table's presence and skip its initialization if desired. |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 812 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 813 | It is legal though generally not very useful to reload built-in or |
| 814 | dynamically loaded modules, except for \refmodule{sys}, |
| 815 | \refmodule[main]{__main__} and \refmodule[builtin]{__builtin__}. In |
| 816 | many cases, however, extension modules are not designed to be |
| 817 | initialized more than once, and may fail in arbitrary ways when |
| 818 | reloaded. |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 819 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 820 | If a module imports objects from another module using \keyword{from} |
| 821 | \ldots{} \keyword{import} \ldots{}, calling \function{reload()} for |
| 822 | the other module does not redefine the objects imported from it --- |
| 823 | one way around this is to re-execute the \keyword{from} statement, |
| 824 | another is to use \keyword{import} and qualified names |
| 825 | (\var{module}.\var{name}) instead. |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 826 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 827 | If a module instantiates instances of a class, reloading the module |
| 828 | that defines the class does not affect the method definitions of the |
| 829 | instances --- they continue to use the old class definition. The |
| 830 | same is true for derived classes. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 831 | \end{funcdesc} |
| 832 | |
| 833 | \begin{funcdesc}{repr}{object} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 834 | Return a string containing a printable representation of an object. |
| 835 | This is the same value yielded by conversions (reverse quotes). |
| 836 | It is sometimes useful to be able to access this operation as an |
| 837 | ordinary function. For many types, this function makes an attempt |
| 838 | to return a string that would yield an object with the same value |
| 839 | when passed to \function{eval()}. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 840 | \end{funcdesc} |
| 841 | |
Raymond Hettinger | 85c20a4 | 2003-11-06 14:06:48 +0000 | [diff] [blame] | 842 | \begin{funcdesc}{reversed}{seq} |
| 843 | Return a reverse iterator. \var{seq} must be an object which |
| 844 | supports the sequence protocol (the __len__() method and the |
| 845 | \method{__getitem__()} method with integer arguments starting at |
| 846 | \code{0}). |
| 847 | \versionadded{2.4} |
| 848 | \end{funcdesc} |
| 849 | |
Fred Drake | 607f802 | 1998-08-24 20:30:07 +0000 | [diff] [blame] | 850 | \begin{funcdesc}{round}{x\optional{, n}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 851 | Return the floating point value \var{x} rounded to \var{n} digits |
| 852 | after the decimal point. If \var{n} is omitted, it defaults to zero. |
| 853 | The result is a floating point number. Values are rounded to the |
| 854 | closest multiple of 10 to the power minus \var{n}; if two multiples |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 855 | are equally close, rounding is done away from 0 (so. for example, |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 856 | \code{round(0.5)} is \code{1.0} and \code{round(-0.5)} is \code{-1.0}). |
| 857 | \end{funcdesc} |
| 858 | |
Raymond Hettinger | a690a99 | 2003-11-16 16:17:49 +0000 | [diff] [blame] | 859 | \begin{funcdesc}{set}{\optional{iterable}} |
| 860 | Return a set whose elements are taken from \var{iterable}. The elements |
| 861 | must be immutable. To represent sets of sets, the inner sets should |
| 862 | be \class{frozenset} objects. If \var{iterable} is not specified, |
| 863 | returns a new empty set, \code{set([])}. |
| 864 | \versionadded{2.4} |
| 865 | \end{funcdesc} |
| 866 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 867 | \begin{funcdesc}{setattr}{object, name, value} |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 868 | This is the counterpart of \function{getattr()}. The arguments are an |
Fred Drake | 607f802 | 1998-08-24 20:30:07 +0000 | [diff] [blame] | 869 | object, a string and an arbitrary value. The string may name an |
| 870 | existing attribute or a new attribute. The function assigns the |
| 871 | value to the attribute, provided the object allows it. For example, |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 872 | \code{setattr(\var{x}, '\var{foobar}', 123)} is equivalent to |
| 873 | \code{\var{x}.\var{foobar} = 123}. |
| 874 | \end{funcdesc} |
| 875 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 876 | \begin{funcdesc}{slice}{\optional{start,} stop\optional{, step}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 877 | Return a slice object representing the set of indices specified by |
| 878 | \code{range(\var{start}, \var{stop}, \var{step})}. The \var{start} |
Fred Drake | 2884d6d | 2003-07-02 12:27:43 +0000 | [diff] [blame] | 879 | and \var{step} arguments default to \code{None}. Slice objects have |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 880 | read-only data attributes \member{start}, \member{stop} and |
| 881 | \member{step} which merely return the argument values (or their |
| 882 | default). They have no other explicit functionality; however they |
| 883 | are used by Numerical Python\index{Numerical Python} and other third |
| 884 | party extensions. Slice objects are also generated when extended |
| 885 | indexing syntax is used. For example: \samp{a[start:stop:step]} or |
| 886 | \samp{a[start:stop, i]}. |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 887 | \end{funcdesc} |
| 888 | |
Raymond Hettinger | 64958a1 | 2003-12-17 20:43:33 +0000 | [diff] [blame] | 889 | \begin{funcdesc}{sorted(\var{iterable}\optional{, \var{cmp}=None |
| 890 | \optional{, \var{key}=None |
| 891 | \optional{, \var{reverse}=False}}})} |
| 892 | Return a new sorted list from the items in \var{iterable}. |
| 893 | The optional arguments \var{cmp}, \var{key}, and \var{reverse} |
| 894 | have the same meaning as those for the \method{list.sort()} method. |
| 895 | \versionadded{2.4} |
| 896 | \end{funcdesc} |
| 897 | |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 898 | \begin{funcdesc}{staticmethod}{function} |
| 899 | Return a static method for \var{function}. |
| 900 | |
| 901 | A static method does not receive an implicit first argument. |
| 902 | To declare a static method, use this idiom: |
| 903 | |
| 904 | \begin{verbatim} |
| 905 | class C: |
| 906 | def f(arg1, arg2, ...): ... |
| 907 | f = staticmethod(f) |
| 908 | \end{verbatim} |
| 909 | |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 910 | It can be called either on the class (such as \code{C.f()}) or on an |
| 911 | instance (such as \code{C().f()}). The instance is ignored except |
| 912 | for its class. |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 913 | |
Fred Drake | f91888b | 2003-06-26 03:11:57 +0000 | [diff] [blame] | 914 | Static methods in Python are similar to those found in Java or \Cpp. |
| 915 | For a more advanced concept, see \function{classmethod()} in this |
| 916 | section. |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 917 | \versionadded{2.2} |
| 918 | \end{funcdesc} |
| 919 | |
Raymond Hettinger | e3d5f98 | 2003-12-07 11:24:03 +0000 | [diff] [blame] | 920 | \begin{funcdesc}{str}{\optional{object}} |
| 921 | Return a string containing a nicely printable representation of an |
| 922 | object. For strings, this returns the string itself. The |
| 923 | difference with \code{repr(\var{object})} is that |
| 924 | \code{str(\var{object})} does not always attempt to return a string |
| 925 | that is acceptable to \function{eval()}; its goal is to return a |
| 926 | printable string. If no argument is given, returns the empty |
| 927 | string, \code{''}. |
| 928 | \end{funcdesc} |
| 929 | |
Fred Drake | 282be3a | 2003-04-22 14:52:08 +0000 | [diff] [blame] | 930 | \begin{funcdesc}{sum}{sequence\optional{, start}} |
| 931 | Sums \var{start} and the items of a \var{sequence}, from left to |
| 932 | right, and returns the total. \var{start} defaults to \code{0}. |
| 933 | The \var{sequence}'s items are normally numbers, and are not allowed |
| 934 | to be strings. The fast, correct way to concatenate sequence of |
| 935 | strings is by calling \code{''.join(\var{sequence})}. |
Fred Drake | 2884d6d | 2003-07-02 12:27:43 +0000 | [diff] [blame] | 936 | Note that \code{sum(range(\var{n}), \var{m})} is equivalent to |
| 937 | \code{reduce(operator.add, range(\var{n}), \var{m})} |
Alex Martelli | a70b191 | 2003-04-22 08:12:33 +0000 | [diff] [blame] | 938 | \versionadded{2.3} |
| 939 | \end{funcdesc} |
| 940 | |
Martin v. Löwis | 8bafb2a | 2003-11-18 19:48:57 +0000 | [diff] [blame] | 941 | \begin{funcdesc}{super}{type\optional{, object-or-type}} |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 942 | Return the superclass of \var{type}. If the second argument is omitted |
| 943 | the super object returned is unbound. If the second argument is an |
Fred Drake | 3ede784 | 2003-07-01 16:31:26 +0000 | [diff] [blame] | 944 | object, \code{isinstance(\var{obj}, \var{type})} must be true. If |
| 945 | the second argument is a type, \code{issubclass(\var{type2}, |
| 946 | \var{type})} must be true. |
| 947 | \function{super()} only works for new-style classes. |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 948 | |
| 949 | A typical use for calling a cooperative superclass method is: |
| 950 | \begin{verbatim} |
| 951 | class C(B): |
| 952 | def meth(self, arg): |
| 953 | super(C, self).meth(arg) |
| 954 | \end{verbatim} |
| 955 | \versionadded{2.2} |
| 956 | \end{funcdesc} |
| 957 | |
Tim Peters | 1fc240e | 2001-10-26 05:06:50 +0000 | [diff] [blame] | 958 | \begin{funcdesc}{tuple}{\optional{sequence}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 959 | Return a tuple whose items are the same and in the same order as |
| 960 | \var{sequence}'s items. \var{sequence} may be a sequence, a |
| 961 | container that supports iteration, or an iterator object. |
| 962 | If \var{sequence} is already a tuple, it |
| 963 | is returned unchanged. For instance, \code{tuple('abc')} returns |
Raymond Hettinger | 7e43110 | 2003-09-22 15:00:55 +0000 | [diff] [blame] | 964 | \code{('a', 'b', 'c')} and \code{tuple([1, 2, 3])} returns |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 965 | \code{(1, 2, 3)}. If no argument is given, returns a new empty |
| 966 | tuple, \code{()}. |
Guido van Rossum | b8b264b | 1994-08-12 13:13:50 +0000 | [diff] [blame] | 967 | \end{funcdesc} |
| 968 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 969 | \begin{funcdesc}{type}{object} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 970 | Return the type of an \var{object}. The return value is a |
| 971 | type\obindex{type} object. The standard module |
| 972 | \module{types}\refstmodindex{types} defines names for all built-in |
Fred Drake | 9482d25 | 2002-11-01 21:33:44 +0000 | [diff] [blame] | 973 | types that don't already have built-in names. |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 974 | For instance: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 975 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 976 | \begin{verbatim} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 977 | >>> import types |
Fred Drake | 9482d25 | 2002-11-01 21:33:44 +0000 | [diff] [blame] | 978 | >>> x = 'abc' |
| 979 | >>> if type(x) is str: print "It's a string" |
| 980 | ... |
| 981 | It's a string |
| 982 | >>> def f(): pass |
| 983 | ... |
| 984 | >>> if type(f) is types.FunctionType: print "It's a function" |
| 985 | ... |
| 986 | It's a function |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 987 | \end{verbatim} |
Fred Drake | 9482d25 | 2002-11-01 21:33:44 +0000 | [diff] [blame] | 988 | |
| 989 | The \function{isinstance()} built-in function is recommended for |
| 990 | testing the type of an object. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 991 | \end{funcdesc} |
Guido van Rossum | 68cfbe7 | 1994-02-24 11:28:27 +0000 | [diff] [blame] | 992 | |
Fred Drake | 33d5184 | 2000-04-06 14:43:12 +0000 | [diff] [blame] | 993 | \begin{funcdesc}{unichr}{i} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 994 | Return the Unicode string of one character whose Unicode code is the |
| 995 | integer \var{i}. For example, \code{unichr(97)} returns the string |
| 996 | \code{u'a'}. This is the inverse of \function{ord()} for Unicode |
| 997 | strings. The argument must be in the range [0..65535], inclusive. |
| 998 | \exception{ValueError} is raised otherwise. |
| 999 | \versionadded{2.0} |
Fred Drake | 33d5184 | 2000-04-06 14:43:12 +0000 | [diff] [blame] | 1000 | \end{funcdesc} |
| 1001 | |
Raymond Hettinger | 3985df2 | 2003-06-11 08:16:06 +0000 | [diff] [blame] | 1002 | \begin{funcdesc}{unicode}{\optional{object\optional{, encoding |
| 1003 | \optional{, errors}}}} |
Marc-André Lemburg | b5507ec | 2001-10-19 12:02:29 +0000 | [diff] [blame] | 1004 | Return the Unicode string version of \var{object} using one of the |
| 1005 | following modes: |
| 1006 | |
| 1007 | If \var{encoding} and/or \var{errors} are given, \code{unicode()} |
| 1008 | will decode the object which can either be an 8-bit string or a |
| 1009 | character buffer using the codec for \var{encoding}. The |
Fred Drake | 4254cbd | 2002-07-09 05:25:46 +0000 | [diff] [blame] | 1010 | \var{encoding} parameter is a string giving the name of an encoding; |
| 1011 | if the encoding is not known, \exception{LookupError} is raised. |
Marc-André Lemburg | b5507ec | 2001-10-19 12:02:29 +0000 | [diff] [blame] | 1012 | Error handling is done according to \var{errors}; this specifies the |
| 1013 | treatment of characters which are invalid in the input encoding. If |
| 1014 | \var{errors} is \code{'strict'} (the default), a |
| 1015 | \exception{ValueError} is raised on errors, while a value of |
| 1016 | \code{'ignore'} causes errors to be silently ignored, and a value of |
| 1017 | \code{'replace'} causes the official Unicode replacement character, |
| 1018 | \code{U+FFFD}, to be used to replace input characters which cannot |
| 1019 | be decoded. See also the \refmodule{codecs} module. |
| 1020 | |
| 1021 | If no optional parameters are given, \code{unicode()} will mimic the |
| 1022 | behaviour of \code{str()} except that it returns Unicode strings |
Fred Drake | 50e1286 | 2002-07-08 14:29:05 +0000 | [diff] [blame] | 1023 | instead of 8-bit strings. More precisely, if \var{object} is a |
| 1024 | Unicode string or subclass it will return that Unicode string without |
Fred Drake | 78e057a | 2002-06-29 16:06:47 +0000 | [diff] [blame] | 1025 | any additional decoding applied. |
| 1026 | |
| 1027 | For objects which provide a \method{__unicode__()} method, it will |
| 1028 | call this method without arguments to create a Unicode string. For |
| 1029 | all other objects, the 8-bit string version or representation is |
| 1030 | requested and then converted to a Unicode string using the codec for |
| 1031 | the default encoding in \code{'strict'} mode. |
| 1032 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 1033 | \versionadded{2.0} |
Fred Drake | 78e057a | 2002-06-29 16:06:47 +0000 | [diff] [blame] | 1034 | \versionchanged[Support for \method{__unicode__()} added]{2.2} |
Fred Drake | 33d5184 | 2000-04-06 14:43:12 +0000 | [diff] [blame] | 1035 | \end{funcdesc} |
| 1036 | |
Guido van Rossum | 6bb1adc | 1995-03-13 10:03:32 +0000 | [diff] [blame] | 1037 | \begin{funcdesc}{vars}{\optional{object}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 1038 | Without arguments, return a dictionary corresponding to the current |
| 1039 | local symbol table. With a module, class or class instance object |
| 1040 | as argument (or anything else that has a \member{__dict__} |
| 1041 | attribute), returns a dictionary corresponding to the object's |
| 1042 | symbol table. The returned dictionary should not be modified: the |
| 1043 | effects on the corresponding symbol table are undefined.\footnote{ |
| 1044 | In the current implementation, local variable bindings cannot |
| 1045 | normally be affected this way, but variables retrieved from |
| 1046 | other scopes (such as modules) can be. This may change.} |
Guido van Rossum | 1738311 | 1994-04-21 10:32:28 +0000 | [diff] [blame] | 1047 | \end{funcdesc} |
| 1048 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 1049 | \begin{funcdesc}{xrange}{\optional{start,} stop\optional{, step}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 1050 | This function is very similar to \function{range()}, but returns an |
| 1051 | ``xrange object'' instead of a list. This is an opaque sequence |
| 1052 | type which yields the same values as the corresponding list, without |
| 1053 | actually storing them all simultaneously. The advantage of |
| 1054 | \function{xrange()} over \function{range()} is minimal (since |
| 1055 | \function{xrange()} still has to create the values when asked for |
| 1056 | them) except when a very large range is used on a memory-starved |
| 1057 | machine or when all of the range's elements are never used (such as |
| 1058 | when the loop is usually terminated with \keyword{break}). |
Guido van Rossum | 68cfbe7 | 1994-02-24 11:28:27 +0000 | [diff] [blame] | 1059 | \end{funcdesc} |
Barry Warsaw | faefa2a | 2000-08-03 15:46:17 +0000 | [diff] [blame] | 1060 | |
Raymond Hettinger | eaef615 | 2003-08-02 07:42:57 +0000 | [diff] [blame] | 1061 | \begin{funcdesc}{zip}{\optional{seq1, \moreargs}} |
Fred Drake | 5172adc | 2001-12-03 18:35:05 +0000 | [diff] [blame] | 1062 | This function returns a list of tuples, where the \var{i}-th tuple contains |
Raymond Hettinger | eaef615 | 2003-08-02 07:42:57 +0000 | [diff] [blame] | 1063 | the \var{i}-th element from each of the argument sequences. |
| 1064 | The returned list is truncated in length to the length of |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 1065 | the shortest argument sequence. When there are multiple argument |
| 1066 | sequences which are all of the same length, \function{zip()} is |
| 1067 | similar to \function{map()} with an initial argument of \code{None}. |
| 1068 | With a single sequence argument, it returns a list of 1-tuples. |
Raymond Hettinger | eaef615 | 2003-08-02 07:42:57 +0000 | [diff] [blame] | 1069 | With no arguments, it returns an empty list. |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 1070 | \versionadded{2.0} |
Raymond Hettinger | eaef615 | 2003-08-02 07:42:57 +0000 | [diff] [blame] | 1071 | |
| 1072 | \versionchanged[Formerly, \function{zip()} required at least one argument |
| 1073 | and \code{zip()} raised a \exception{TypeError} instead of returning |
Raymond Hettinger | d446230 | 2003-11-26 17:52:45 +0000 | [diff] [blame] | 1074 | an empty list.]{2.4} |
Fred Drake | 8b168ba | 2000-08-03 17:29:13 +0000 | [diff] [blame] | 1075 | \end{funcdesc} |
Raymond Hettinger | bd93b3e | 2003-11-25 21:48:21 +0000 | [diff] [blame] | 1076 | |
| 1077 | |
| 1078 | % --------------------------------------------------------------------------- |
| 1079 | |
| 1080 | |
| 1081 | \section{Non-essential Built-in Functions \label{non-essential-built-in-funcs}} |
| 1082 | |
| 1083 | There are several built-in functions that are no longer essential to learn, |
| 1084 | know or use in modern Python programming. They have been kept here to |
| 1085 | maintain backwards compatability with programs written for older versions |
| 1086 | of Python. |
| 1087 | |
| 1088 | Python programmers, trainers, students and bookwriters should feel free to |
| 1089 | bypass these functions without concerns about missing something important. |
| 1090 | |
| 1091 | |
| 1092 | \setindexsubitem{(non-essential built-in functions)} |
| 1093 | |
| 1094 | \begin{funcdesc}{apply}{function, args\optional{, keywords}} |
| 1095 | The \var{function} argument must be a callable object (a |
| 1096 | user-defined or built-in function or method, or a class object) and |
| 1097 | the \var{args} argument must be a sequence. The \var{function} is |
| 1098 | called with \var{args} as the argument list; the number of arguments |
| 1099 | is the length of the tuple. |
| 1100 | If the optional \var{keywords} argument is present, it must be a |
| 1101 | dictionary whose keys are strings. It specifies keyword arguments |
| 1102 | to be added to the end of the argument list. |
| 1103 | Calling \function{apply()} is different from just calling |
| 1104 | \code{\var{function}(\var{args})}, since in that case there is always |
| 1105 | exactly one argument. The use of \function{apply()} is equivalent |
| 1106 | to \code{\var{function}(*\var{args}, **\var{keywords})}. |
| 1107 | Use of \function{apply()} is not necessary since the ``extended call |
| 1108 | syntax,'' as used in the last example, is completely equivalent. |
| 1109 | |
| 1110 | \deprecated{2.3}{Use the extended call syntax instead, as described |
| 1111 | above.} |
| 1112 | \end{funcdesc} |
| 1113 | |
| 1114 | \begin{funcdesc}{buffer}{object\optional{, offset\optional{, size}}} |
| 1115 | The \var{object} argument must be an object that supports the buffer |
| 1116 | call interface (such as strings, arrays, and buffers). A new buffer |
| 1117 | object will be created which references the \var{object} argument. |
| 1118 | The buffer object will be a slice from the beginning of \var{object} |
| 1119 | (or from the specified \var{offset}). The slice will extend to the |
| 1120 | end of \var{object} (or will have a length given by the \var{size} |
| 1121 | argument). |
| 1122 | \end{funcdesc} |
| 1123 | |
| 1124 | \begin{funcdesc}{coerce}{x, y} |
| 1125 | Return a tuple consisting of the two numeric arguments converted to |
| 1126 | a common type, using the same rules as used by arithmetic |
| 1127 | operations. |
| 1128 | \end{funcdesc} |
| 1129 | |
| 1130 | \begin{funcdesc}{intern}{string} |
| 1131 | Enter \var{string} in the table of ``interned'' strings and return |
| 1132 | the interned string -- which is \var{string} itself or a copy. |
| 1133 | Interning strings is useful to gain a little performance on |
| 1134 | dictionary lookup -- if the keys in a dictionary are interned, and |
| 1135 | the lookup key is interned, the key comparisons (after hashing) can |
| 1136 | be done by a pointer compare instead of a string compare. Normally, |
| 1137 | the names used in Python programs are automatically interned, and |
| 1138 | the dictionaries used to hold module, class or instance attributes |
| 1139 | have interned keys. \versionchanged[Interned strings are not |
| 1140 | immortal (like they used to be in Python 2.2 and before); |
| 1141 | you must keep a reference to the return value of \function{intern()} |
| 1142 | around to benefit from it]{2.3} |
| 1143 | \end{funcdesc} |