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 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 63 | \begin{funcdesc}{apply}{function, args\optional{, keywords}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 64 | The \var{function} argument must be a callable object (a |
| 65 | user-defined or built-in function or method, or a class object) and |
Fred Drake | 66ded52 | 2001-11-07 06:22:25 +0000 | [diff] [blame] | 66 | the \var{args} argument must be a sequence. The \var{function} is |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 67 | called with \var{args} as the argument list; the number of arguments |
Raymond Hettinger | d918884 | 2002-09-04 23:52:42 +0000 | [diff] [blame] | 68 | is the length of the tuple. |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 69 | If the optional \var{keywords} argument is present, it must be a |
| 70 | dictionary whose keys are strings. It specifies keyword arguments |
| 71 | to be added to the end of the the argument list. |
Fred Drake | 66ded52 | 2001-11-07 06:22:25 +0000 | [diff] [blame] | 72 | Calling \function{apply()} is different from just calling |
Fred Drake | 0b66310 | 2001-11-07 06:28:47 +0000 | [diff] [blame] | 73 | \code{\var{function}(\var{args})}, since in that case there is always |
Fred Drake | 66ded52 | 2001-11-07 06:22:25 +0000 | [diff] [blame] | 74 | exactly one argument. The use of \function{apply()} is equivalent |
| 75 | to \code{\var{function}(*\var{args}, **\var{keywords})}. |
Fred Drake | 5ec486b | 2002-08-22 14:27:35 +0000 | [diff] [blame] | 76 | Use of \function{apply()} is not necessary since the ``extended call |
| 77 | syntax,'' as used in the last example, is completely equivalent. |
Fred Drake | 45e482f | 2003-01-02 04:54:04 +0000 | [diff] [blame] | 78 | |
| 79 | \deprecated{2.3}{Use the extended call syntax instead, as described |
| 80 | above.} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 81 | \end{funcdesc} |
| 82 | |
Guido van Rossum | 77f6a65 | 2002-04-03 22:41:51 +0000 | [diff] [blame] | 83 | \begin{funcdesc}{bool}{x} |
| 84 | Convert a value to a Boolean, using the standard truth testing |
| 85 | procedure. If \code{x} is false, this returns \code{False}; |
| 86 | otherwise it returns \code{True}. \code{bool} is also a class, |
| 87 | which is a subclass of \code{int}. Class \code{bool} cannot be |
| 88 | subclassed further. Its only instances are \code{False} and |
| 89 | \code{True}. |
| 90 | \indexii{Boolean}{type} |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 91 | \versionadded{2.2.1} |
Guido van Rossum | 77f6a65 | 2002-04-03 22:41:51 +0000 | [diff] [blame] | 92 | \end{funcdesc} |
| 93 | |
Guido van Rossum | 8be2296 | 1999-03-19 19:10:14 +0000 | [diff] [blame] | 94 | \begin{funcdesc}{buffer}{object\optional{, offset\optional{, size}}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 95 | The \var{object} argument must be an object that supports the buffer |
| 96 | call interface (such as strings, arrays, and buffers). A new buffer |
| 97 | object will be created which references the \var{object} argument. |
| 98 | The buffer object will be a slice from the beginning of \var{object} |
| 99 | (or from the specified \var{offset}). The slice will extend to the |
| 100 | end of \var{object} (or will have a length given by the \var{size} |
| 101 | argument). |
Guido van Rossum | 8be2296 | 1999-03-19 19:10:14 +0000 | [diff] [blame] | 102 | \end{funcdesc} |
| 103 | |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 104 | \begin{funcdesc}{callable}{object} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 105 | Return true if the \var{object} argument appears callable, false if |
| 106 | not. If this returns true, it is still possible that a call fails, |
| 107 | but if it is false, calling \var{object} will never succeed. Note |
| 108 | that classes are callable (calling a class returns a new instance); |
| 109 | class instances are callable if they have a \method{__call__()} |
| 110 | method. |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 111 | \end{funcdesc} |
| 112 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 113 | \begin{funcdesc}{chr}{i} |
| 114 | Return a string of one character whose \ASCII{} code is the integer |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 115 | \var{i}. For example, \code{chr(97)} returns the string \code{'a'}. |
| 116 | This is the inverse of \function{ord()}. The argument must be in |
| 117 | the range [0..255], inclusive; \exception{ValueError} will be raised |
| 118 | if \var{i} is outside that range. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 119 | \end{funcdesc} |
| 120 | |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 121 | \begin{funcdesc}{classmethod}{function} |
| 122 | Return a class method for \var{function}. |
| 123 | |
| 124 | A class method receives the class as implicit first argument, |
| 125 | just like an instance method receives the instance. |
| 126 | To declare a class method, use this idiom: |
| 127 | |
| 128 | \begin{verbatim} |
| 129 | class C: |
| 130 | def f(cls, arg1, arg2, ...): ... |
| 131 | f = classmethod(f) |
| 132 | \end{verbatim} |
| 133 | |
| 134 | It can be called either on the class (e.g. C.f()) or on an instance |
| 135 | (e.g. C().f()). The instance is ignored except for its class. |
| 136 | If a class method is called for a derived class, the derived class |
| 137 | object is passed as the implied first argument. |
| 138 | |
| 139 | Class methods are different than C++ or Java static methods. |
| 140 | If you want those, see \ref{staticmethod}. |
| 141 | \versionadded{2.2} |
| 142 | \end{funcdesc} |
| 143 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 144 | \begin{funcdesc}{cmp}{x, y} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 145 | Compare the two objects \var{x} and \var{y} and return an integer |
| 146 | according to the outcome. The return value is negative if \code{\var{x} |
| 147 | < \var{y}}, zero if \code{\var{x} == \var{y}} and strictly positive if |
| 148 | \code{\var{x} > \var{y}}. |
| 149 | \end{funcdesc} |
| 150 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 151 | \begin{funcdesc}{coerce}{x, y} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 152 | Return a tuple consisting of the two numeric arguments converted to |
| 153 | a common type, using the same rules as used by arithmetic |
| 154 | operations. |
| 155 | \end{funcdesc} |
| 156 | |
Tim Peters | 32f453e | 2001-09-03 08:35:41 +0000 | [diff] [blame] | 157 | \begin{funcdesc}{compile}{string, filename, kind\optional{, |
Michael W. Hudson | 53da317 | 2001-08-27 20:02:17 +0000 | [diff] [blame] | 158 | flags\optional{, dont_inherit}}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 159 | Compile the \var{string} into a code object. Code objects can be |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 160 | executed by an \keyword{exec} statement or evaluated by a call to |
| 161 | \function{eval()}. The \var{filename} argument should |
Guido van Rossum | 0d68246 | 2001-09-29 14:28:52 +0000 | [diff] [blame] | 162 | 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] | 163 | if it wasn't read from a file (\code{'<string>'} is commonly used). |
| 164 | The \var{kind} argument specifies what kind of code must be |
| 165 | compiled; it can be \code{'exec'} if \var{string} consists of a |
| 166 | sequence of statements, \code{'eval'} if it consists of a single |
| 167 | expression, or \code{'single'} if it consists of a single |
| 168 | interactive statement (in the latter case, expression statements |
| 169 | that evaluate to something else than \code{None} will printed). |
Michael W. Hudson | 53da317 | 2001-08-27 20:02:17 +0000 | [diff] [blame] | 170 | |
Guido van Rossum | 0d68246 | 2001-09-29 14:28:52 +0000 | [diff] [blame] | 171 | When compiling multi-line statements, two caveats apply: line |
| 172 | endings must be represented by a single newline character |
| 173 | (\code{'\e n'}), and the input must be terminated by at least one |
| 174 | newline character. If line endings are represented by |
| 175 | \code{'\e r\e n'}, use the string \method{replace()} method to |
| 176 | change them into \code{'\e n'}. |
| 177 | |
| 178 | The optional arguments \var{flags} and \var{dont_inherit} |
Michael W. Hudson | 53da317 | 2001-08-27 20:02:17 +0000 | [diff] [blame] | 179 | (which are new in Python 2.2) control which future statements (see |
| 180 | \pep{236}) affect the compilation of \var{string}. If neither is |
| 181 | present (or both are zero) the code is compiled with those future |
| 182 | statements that are in effect in the code that is calling compile. |
| 183 | If the \var{flags} argument is given and \var{dont_inherit} is not |
| 184 | (or is zero) then the future statements specified by the \var{flags} |
| 185 | argument are used in addition to those that would be used anyway. |
| 186 | If \var{dont_inherit} is a non-zero integer then the \var{flags} |
| 187 | argument is it -- the future statements in effect around the call to |
| 188 | compile are ignored. |
| 189 | |
| 190 | Future statemants are specified by bits which can be bitwise or-ed |
| 191 | together to specify multiple statements. The bitfield required to |
| 192 | specify a given feature can be found as the \member{compiler_flag} |
| 193 | attribute on the \class{_Feature} instance in the |
| 194 | \module{__future__} module. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 195 | \end{funcdesc} |
| 196 | |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 197 | \begin{funcdesc}{complex}{real\optional{, imag}} |
Guido van Rossum | cb1f242 | 1999-03-25 21:23:26 +0000 | [diff] [blame] | 198 | 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] | 199 | convert a string or number to a complex number. If the first |
| 200 | parameter is a string, it will be interpreted as a complex number |
| 201 | and the function must be called without a second parameter. The |
| 202 | second parameter can never be a string. |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 203 | Each argument may be any numeric type (including complex). |
| 204 | If \var{imag} is omitted, it defaults to zero and the function |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 205 | serves as a numeric conversion function like \function{int()}, |
Fred Drake | 526c7a0 | 2001-12-13 19:52:22 +0000 | [diff] [blame] | 206 | \function{long()} and \function{float()}. |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 207 | \end{funcdesc} |
| 208 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 209 | \begin{funcdesc}{delattr}{object, name} |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 210 | This is a relative of \function{setattr()}. The arguments are an |
Guido van Rossum | 1efbb0f | 1994-08-16 22:15:11 +0000 | [diff] [blame] | 211 | object and a string. The string must be the name |
| 212 | of one of the object's attributes. The function deletes |
| 213 | the named attribute, provided the object allows it. For example, |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 214 | \code{delattr(\var{x}, '\var{foobar}')} is equivalent to |
Guido van Rossum | 1efbb0f | 1994-08-16 22:15:11 +0000 | [diff] [blame] | 215 | \code{del \var{x}.\var{foobar}}. |
| 216 | \end{funcdesc} |
| 217 | |
Tim Peters | a427a2b | 2001-10-29 22:25:45 +0000 | [diff] [blame] | 218 | \begin{funcdesc}{dict}{\optional{mapping-or-sequence}} |
Just van Rossum | a797d81 | 2002-11-23 09:45:04 +0000 | [diff] [blame] | 219 | Return a new dictionary initialized from an optional positional |
| 220 | argument or from a set of keyword arguments. |
| 221 | If no arguments are given, return a new empty dictionary. |
| 222 | If the positional argument is a mapping object, return a dictionary |
| 223 | mapping the same keys to the same values as does the mapping object. |
| 224 | Otherwise the positional argument must be a sequence, a container that |
| 225 | supports iteration, or an iterator object. The elements of the argument |
| 226 | 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] | 227 | exactly two objects. The first is used as a key in the new dictionary, |
| 228 | and the second as the key's value. If a given key is seen more than |
| 229 | once, the last value associated with it is retained in the new |
| 230 | dictionary. |
Just van Rossum | a797d81 | 2002-11-23 09:45:04 +0000 | [diff] [blame] | 231 | |
| 232 | If keyword arguments are given, the keywords themselves with their |
| 233 | associated values are added as items to the dictionary. If a key |
| 234 | is specified both in the positional argument and as a keyword argument, |
| 235 | the value associated with the keyword is retained in the dictionary. |
Tim Peters | 1fc240e | 2001-10-26 05:06:50 +0000 | [diff] [blame] | 236 | For example, these all return a dictionary equal to |
Just van Rossum | a797d81 | 2002-11-23 09:45:04 +0000 | [diff] [blame] | 237 | \code{\{"one": 2, "two": 3\}}: |
Fred Drake | ef7d08a | 2001-10-26 15:04:33 +0000 | [diff] [blame] | 238 | |
| 239 | \begin{itemize} |
Just van Rossum | a797d81 | 2002-11-23 09:45:04 +0000 | [diff] [blame] | 240 | \item \code{dict(\{'one': 2, 'two': 3\})} |
| 241 | \item \code{dict(\{'one': 2, 'two': 3\}.items())} |
| 242 | \item \code{dict(\{'one': 2, 'two': 3\}.iteritems())} |
| 243 | \item \code{dict(zip(('one', 'two'), (2, 3)))} |
| 244 | \item \code{dict([['two', 3], ['one', 2]])} |
| 245 | \item \code{dict(one=2, two=3)} |
| 246 | \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] | 247 | \end{itemize} |
Fred Drake | da8a6dd | 2002-03-06 02:29:30 +0000 | [diff] [blame] | 248 | |
| 249 | \versionadded{2.2} |
Fred Drake | 6e596b6 | 2002-11-23 15:02:13 +0000 | [diff] [blame] | 250 | \versionchanged[Support for building a dictionary from keyword |
| 251 | arguments added]{2.3} |
Tim Peters | 1fc240e | 2001-10-26 05:06:50 +0000 | [diff] [blame] | 252 | \end{funcdesc} |
| 253 | |
Fred Drake | 6b303b4 | 1998-04-16 22:10:27 +0000 | [diff] [blame] | 254 | \begin{funcdesc}{dir}{\optional{object}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 255 | Without arguments, return the list of names in the current local |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 256 | symbol table. With an argument, attempts to return a list of valid |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 257 | attributes for that object. This information is gleaned from the |
Fred Drake | 3570551 | 2001-12-03 17:32:27 +0000 | [diff] [blame] | 258 | object's \member{__dict__} attribute, if defined, and from the class |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 259 | or type object. The list is not necessarily complete. |
| 260 | If the object is a module object, the list contains the names of the |
| 261 | module's attributes. |
| 262 | If the object is a type or class object, |
| 263 | the list contains the names of its attributes, |
| 264 | and recursively of the attributes of its bases. |
| 265 | Otherwise, the list contains the object's attributes' names, |
| 266 | the names of its class's attributes, |
| 267 | and recursively of the attributes of its class's base classes. |
| 268 | The resulting list is sorted alphabetically. |
| 269 | For example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 270 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 271 | \begin{verbatim} |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 272 | >>> import struct |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 273 | >>> dir() |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 274 | ['__builtins__', '__doc__', '__name__', 'struct'] |
| 275 | >>> dir(struct) |
| 276 | ['__doc__', '__name__', 'calcsize', 'error', 'pack', 'unpack'] |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 277 | \end{verbatim} |
Tim Peters | 9f4341b | 2002-02-23 04:40:15 +0000 | [diff] [blame] | 278 | |
| 279 | \note{Because \function{dir()} is supplied primarily as a convenience |
| 280 | for use at an interactive prompt, |
| 281 | it tries to supply an interesting set of names more than it tries to |
| 282 | supply a rigorously or consistently defined set of names, |
| 283 | and its detailed behavior may change across releases.} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 284 | \end{funcdesc} |
| 285 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 286 | \begin{funcdesc}{divmod}{a, b} |
Raymond Hettinger | 6cf09f0 | 2002-05-21 18:19:49 +0000 | [diff] [blame] | 287 | Take two (non complex) numbers as arguments and return a pair of numbers |
| 288 | consisting of their quotient and remainder when using long division. With |
| 289 | mixed operand types, the rules for binary arithmetic operators apply. For |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 290 | plain and long integers, the result is the same as |
| 291 | \code{(\var{a} / \var{b}, \var{a} \%{} \var{b})}. |
Fred Drake | 1ea7c75 | 1999-05-06 14:46:35 +0000 | [diff] [blame] | 292 | For floating point numbers the result is \code{(\var{q}, \var{a} \%{} |
| 293 | \var{b})}, where \var{q} is usually \code{math.floor(\var{a} / |
| 294 | \var{b})} but may be 1 less than that. In any case \code{\var{q} * |
| 295 | \var{b} + \var{a} \%{} \var{b}} is very close to \var{a}, if |
| 296 | \code{\var{a} \%{} \var{b}} is non-zero it has the same sign as |
| 297 | \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] | 298 | |
| 299 | \versionchanged[Using \function{divmod()} with complex numbers is |
| 300 | deprecated]{2.3} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 301 | \end{funcdesc} |
| 302 | |
Fred Drake | 38f7197 | 2002-04-26 20:29:44 +0000 | [diff] [blame] | 303 | \begin{funcdesc}{enumerate}{iterable} |
| 304 | Return an enumerate object. \var{iterable} must be a sequence, an |
| 305 | iterator, or some other object which supports iteration. The |
| 306 | \method{next()} method of the iterator returned by |
| 307 | \function{enumerate()} returns a tuple containing a count (from |
| 308 | zero) and the corresponding value obtained from iterating over |
Fred Drake | 8f53cdc | 2003-05-10 19:46:39 +0000 | [diff] [blame] | 309 | \var{iterable}. \function{enumerate()} is useful for obtaining an |
Fred Drake | 38f7197 | 2002-04-26 20:29:44 +0000 | [diff] [blame] | 310 | indexed series: \code{(0, seq[0])}, \code{(1, seq[1])}, \code{(2, |
| 311 | seq[2])}, \ldots. |
| 312 | \versionadded{2.3} |
| 313 | \end{funcdesc} |
| 314 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 315 | \begin{funcdesc}{eval}{expression\optional{, globals\optional{, locals}}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 316 | The arguments are a string and two optional dictionaries. The |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 317 | \var{expression} argument is parsed and evaluated as a Python |
| 318 | expression (technically speaking, a condition list) using the |
| 319 | \var{globals} and \var{locals} dictionaries as global and local name |
Neal Norwitz | 046b8a7 | 2002-12-17 01:08:06 +0000 | [diff] [blame] | 320 | space. If the \var{globals} dictionary is present and lacks |
| 321 | '__builtins__', the current globals are copied into \var{globals} before |
| 322 | \var{expression} is parsed. This means that \var{expression} |
| 323 | normally has full access to the standard |
| 324 | \refmodule[builtin]{__builtin__} module and restricted environments |
| 325 | 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] | 326 | the \var{globals} dictionary. If both dictionaries are omitted, the |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 327 | expression is executed in the environment where \keyword{eval} is |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 328 | called. The return value is the result of the evaluated expression. |
| 329 | Syntax errors are reported as exceptions. Example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 330 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 331 | \begin{verbatim} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 332 | >>> x = 1 |
| 333 | >>> print eval('x+1') |
| 334 | 2 |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 335 | \end{verbatim} |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 336 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 337 | This function can also be used to execute arbitrary code objects |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 338 | (such as those created by \function{compile()}). In this case pass |
| 339 | a code object instead of a string. The code object must have been |
| 340 | compiled passing \code{'eval'} as the \var{kind} argument. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 341 | |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 342 | Hints: dynamic execution of statements is supported by the |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 343 | \keyword{exec} statement. Execution of statements from a file is |
| 344 | supported by the \function{execfile()} function. The |
| 345 | \function{globals()} and \function{locals()} functions returns the |
| 346 | current global and local dictionary, respectively, which may be |
| 347 | useful to pass around for use by \function{eval()} or |
| 348 | \function{execfile()}. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 349 | \end{funcdesc} |
| 350 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 351 | \begin{funcdesc}{execfile}{file\optional{, globals\optional{, locals}}} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 352 | This function is similar to the |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 353 | \keyword{exec} statement, but parses a file instead of a string. It |
| 354 | is different from the \keyword{import} statement in that it does not |
| 355 | use the module administration --- it reads the file unconditionally |
| 356 | and does not create a new module.\footnote{It is used relatively |
| 357 | rarely so does not warrant being made into a statement.} |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 358 | |
| 359 | The arguments are a file name and two optional dictionaries. The |
| 360 | file is parsed and evaluated as a sequence of Python statements |
| 361 | (similarly to a module) using the \var{globals} and \var{locals} |
Fred Drake | 1349437 | 2000-09-12 16:23:48 +0000 | [diff] [blame] | 362 | dictionaries as global and local namespace. If the \var{locals} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 363 | dictionary is omitted it defaults to the \var{globals} dictionary. |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 364 | If both dictionaries are omitted, the expression is executed in the |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 365 | environment where \function{execfile()} is called. The return value is |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 366 | \code{None}. |
Tim Peters | af5910f | 2001-09-30 06:32:59 +0000 | [diff] [blame] | 367 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 368 | \warning{The default \var{locals} act as described for function |
Tim Peters | af5910f | 2001-09-30 06:32:59 +0000 | [diff] [blame] | 369 | \function{locals()} below: modifications to the default \var{locals} |
| 370 | dictionary should not be attempted. Pass an explicit \var{locals} |
| 371 | dictionary if you need to see effects of the code on \var{locals} after |
| 372 | function \function{execfile()} returns. \function{execfile()} cannot |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 373 | be used reliably to modify a function's locals.} |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 374 | \end{funcdesc} |
| 375 | |
Tim Peters | 2e29bfb | 2001-09-20 19:55:29 +0000 | [diff] [blame] | 376 | \begin{funcdesc}{file}{filename\optional{, mode\optional{, bufsize}}} |
| 377 | Return a new file object (described earlier under Built-in Types). |
| 378 | The first two arguments are the same as for \code{stdio}'s |
| 379 | \cfunction{fopen()}: \var{filename} is the file name to be opened, |
| 380 | \var{mode} indicates how the file is to be opened: \code{'r'} for |
| 381 | reading, \code{'w'} for writing (truncating an existing file), and |
| 382 | \code{'a'} opens it for appending (which on \emph{some} \UNIX{} |
| 383 | systems means that \emph{all} writes append to the end of the file, |
| 384 | regardless of the current seek position). |
| 385 | |
| 386 | Modes \code{'r+'}, \code{'w+'} and \code{'a+'} open the file for |
| 387 | updating (note that \code{'w+'} truncates the file). Append |
| 388 | \code{'b'} to the mode to open the file in binary mode, on systems |
| 389 | that differentiate between binary and text files (else it is |
| 390 | ignored). If the file cannot be opened, \exception{IOError} is |
| 391 | raised. |
Barry Warsaw | 177b4a0 | 2002-05-22 20:39:43 +0000 | [diff] [blame] | 392 | |
| 393 | In addition to the standard \cfunction{fopen()} values \var{mode} |
| 394 | may be \code{'U'} or \code{'rU'}. If Python is built with universal |
| 395 | newline support (the default) the file is opened as a text file, but |
| 396 | lines may be terminated by any of \code{'\e n'}, the Unix end-of-line |
| 397 | convention, |
| 398 | \code{'\e r'}, the Macintosh convention or \code{'\e r\e n'}, the Windows |
| 399 | convention. All of these external representations are seen as |
| 400 | \code{'\e n'} |
| 401 | by the Python program. If Python is built without universal newline support |
| 402 | \var{mode} \code{'U'} is the same as normal text mode. Note that |
| 403 | file objects so opened also have an attribute called |
| 404 | \member{newlines} which has a value of \code{None} (if no newlines |
| 405 | have yet been seen), \code{'\e n'}, \code{'\e r'}, \code{'\e r\e n'}, |
| 406 | or a tuple containing all the newline types seen. |
Tim Peters | 2e29bfb | 2001-09-20 19:55:29 +0000 | [diff] [blame] | 407 | |
| 408 | If \var{mode} is omitted, it defaults to \code{'r'}. When opening a |
| 409 | binary file, you should append \code{'b'} to the \var{mode} value |
| 410 | for improved portability. (It's useful even on systems which don't |
| 411 | treat binary and text files differently, where it serves as |
| 412 | documentation.) |
| 413 | \index{line-buffered I/O}\index{unbuffered I/O}\index{buffer size, I/O} |
| 414 | \index{I/O control!buffering} |
| 415 | The optional \var{bufsize} argument specifies the |
| 416 | file's desired buffer size: 0 means unbuffered, 1 means line |
| 417 | buffered, any other positive value means use a buffer of |
| 418 | (approximately) that size. A negative \var{bufsize} means to use |
| 419 | the system default, which is usually line buffered for for tty |
| 420 | devices and fully buffered for other files. If omitted, the system |
| 421 | default is used.\footnote{ |
| 422 | Specifying a buffer size currently has no effect on systems that |
| 423 | don't have \cfunction{setvbuf()}. The interface to specify the |
| 424 | buffer size is not done using a method that calls |
| 425 | \cfunction{setvbuf()}, because that may dump core when called |
| 426 | after any I/O has been performed, and there's no reliable way to |
| 427 | determine whether this is the case.} |
| 428 | |
| 429 | The \function{file()} constructor is new in Python 2.2. The previous |
| 430 | spelling, \function{open()}, is retained for compatibility, and is an |
| 431 | alias for \function{file()}. |
| 432 | \end{funcdesc} |
| 433 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 434 | \begin{funcdesc}{filter}{function, list} |
Fred Drake | eacdec6 | 2001-05-02 20:19:19 +0000 | [diff] [blame] | 435 | Construct a list from those elements of \var{list} for which |
| 436 | \var{function} returns true. \var{list} may be either a sequence, a |
| 437 | container which supports iteration, or an iterator, If \var{list} |
| 438 | is a string or a tuple, the result also has that type; otherwise it |
| 439 | is always a list. If \var{function} is \code{None}, the identity |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 440 | 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] | 441 | (zero or empty) are removed. |
Martin v. Löwis | 7472336 | 2003-05-31 08:02:38 +0000 | [diff] [blame^] | 442 | |
| 443 | Note that \code{filter(function, list)} equals |
| 444 | \code{[item for item in list if function(item)]} if function is not |
| 445 | \code{None} and \code{[item for item in list if item]} if function is |
| 446 | None. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 447 | \end{funcdesc} |
| 448 | |
| 449 | \begin{funcdesc}{float}{x} |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 450 | 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] | 451 | string, it must contain a possibly signed decimal or floating point |
Fred Drake | 70a66c9 | 1999-02-18 16:08:36 +0000 | [diff] [blame] | 452 | number, possibly embedded in whitespace; this behaves identical to |
| 453 | \code{string.atof(\var{x})}. Otherwise, the argument may be a plain |
| 454 | or long integer or a floating point number, and a floating point |
| 455 | number with the same value (within Python's floating point |
| 456 | precision) is returned. |
| 457 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 458 | \note{When passing in a string, values for NaN\index{NaN} |
Fred Drake | 70a66c9 | 1999-02-18 16:08:36 +0000 | [diff] [blame] | 459 | and Infinity\index{Infinity} may be returned, depending on the |
| 460 | underlying C library. The specific set of strings accepted which |
| 461 | cause these values to be returned depends entirely on the C library |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 462 | and is known to vary.} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 463 | \end{funcdesc} |
| 464 | |
Fred Drake | de5d5ce | 1999-07-22 19:21:45 +0000 | [diff] [blame] | 465 | \begin{funcdesc}{getattr}{object, name\optional{, default}} |
| 466 | Return the value of the named attributed of \var{object}. \var{name} |
| 467 | must be a string. If the string is the name of one of the object's |
| 468 | attributes, the result is the value of that attribute. For example, |
| 469 | \code{getattr(x, 'foobar')} is equivalent to \code{x.foobar}. If the |
| 470 | named attribute does not exist, \var{default} is returned if provided, |
| 471 | otherwise \exception{AttributeError} is raised. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 472 | \end{funcdesc} |
| 473 | |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 474 | \begin{funcdesc}{globals}{} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 475 | Return a dictionary representing the current global symbol table. |
| 476 | This is always the dictionary of the current module (inside a |
| 477 | function or method, this is the module where it is defined, not the |
| 478 | module from which it is called). |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 479 | \end{funcdesc} |
| 480 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 481 | \begin{funcdesc}{hasattr}{object, name} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 482 | The arguments are an object and a string. The result is 1 if the |
| 483 | 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] | 484 | (This is implemented by calling \code{getattr(\var{object}, |
| 485 | \var{name})} and seeing whether it raises an exception or not.) |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 486 | \end{funcdesc} |
| 487 | |
| 488 | \begin{funcdesc}{hash}{object} |
| 489 | 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] | 490 | are integers. They are used to quickly compare dictionary |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 491 | keys during a dictionary lookup. Numeric values that compare equal |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 492 | have the same hash value (even if they are of different types, as is |
| 493 | the case for 1 and 1.0). |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 494 | \end{funcdesc} |
| 495 | |
Fred Drake | 732299f | 2001-12-18 16:31:08 +0000 | [diff] [blame] | 496 | \begin{funcdesc}{help}{\optional{object}} |
| 497 | Invoke the built-in help system. (This function is intended for |
| 498 | interactive use.) If no argument is given, the interactive help |
| 499 | system starts on the interpreter console. If the argument is a |
| 500 | string, then the string is looked up as the name of a module, |
| 501 | function, class, method, keyword, or documentation topic, and a |
| 502 | help page is printed on the console. If the argument is any other |
| 503 | kind of object, a help page on the object is generated. |
Fred Drake | 933f159 | 2002-04-17 12:54:04 +0000 | [diff] [blame] | 504 | \versionadded{2.2} |
Fred Drake | 732299f | 2001-12-18 16:31:08 +0000 | [diff] [blame] | 505 | \end{funcdesc} |
| 506 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 507 | \begin{funcdesc}{hex}{x} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 508 | Convert an integer number (of any size) to a hexadecimal string. |
Guido van Rossum | 5cd7520 | 1997-01-14 18:44:23 +0000 | [diff] [blame] | 509 | The result is a valid Python expression. Note: this always yields |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 510 | an unsigned literal. For example, on a 32-bit machine, |
| 511 | \code{hex(-1)} yields \code{'0xffffffff'}. When evaluated on a |
| 512 | machine with the same word size, this literal is evaluated as -1; at |
| 513 | a different word size, it may turn up as a large positive number or |
| 514 | raise an \exception{OverflowError} exception. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 515 | \end{funcdesc} |
| 516 | |
| 517 | \begin{funcdesc}{id}{object} |
Fred Drake | 8aa3bd9 | 2000-06-29 03:46:46 +0000 | [diff] [blame] | 518 | Return the `identity' of an object. This is an integer (or long |
| 519 | integer) which is guaranteed to be unique and constant for this |
| 520 | object during its lifetime. Two objects whose lifetimes are |
| 521 | disjunct may have the same \function{id()} value. (Implementation |
| 522 | note: this is the address of the object.) |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 523 | \end{funcdesc} |
| 524 | |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 525 | \begin{funcdesc}{input}{\optional{prompt}} |
Guido van Rossum | 777dcc6 | 1998-06-17 15:16:40 +0000 | [diff] [blame] | 526 | Equivalent to \code{eval(raw_input(\var{prompt}))}. |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 527 | \warning{This function is not safe from user errors! It |
Fred Drake | f96e0d2 | 2000-09-09 03:33:42 +0000 | [diff] [blame] | 528 | expects a valid Python expression as input; if the input is not |
| 529 | syntactically valid, a \exception{SyntaxError} will be raised. |
| 530 | Other exceptions may be raised if there is an error during |
| 531 | evaluation. (On the other hand, sometimes this is exactly what you |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 532 | need when writing a quick script for expert use.)} |
Fred Drake | f96e0d2 | 2000-09-09 03:33:42 +0000 | [diff] [blame] | 533 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 534 | If the \refmodule{readline} module was loaded, then |
Fred Drake | f96e0d2 | 2000-09-09 03:33:42 +0000 | [diff] [blame] | 535 | \function{input()} will use it to provide elaborate line editing and |
| 536 | history features. |
| 537 | |
| 538 | Consider using the \function{raw_input()} function for general input |
| 539 | from users. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 540 | \end{funcdesc} |
| 541 | |
Fred Drake | 1e862e8 | 2000-02-17 17:45:52 +0000 | [diff] [blame] | 542 | \begin{funcdesc}{int}{x\optional{, radix}} |
| 543 | Convert a string or number to a plain integer. If the argument is a |
| 544 | string, it must contain a possibly signed decimal number |
Martin v. Löwis | 7472336 | 2003-05-31 08:02:38 +0000 | [diff] [blame^] | 545 | representable as a Python integer, possibly embedded in whitespace. |
| 546 | The \var{radix} parameter gives the base for the |
Fred Drake | 17383b9 | 2000-11-17 19:44:14 +0000 | [diff] [blame] | 547 | conversion and may be any integer in the range [2, 36], or zero. If |
| 548 | \var{radix} is zero, the proper radix is guessed based on the |
| 549 | contents of string; the interpretation is the same as for integer |
| 550 | 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] | 551 | \exception{TypeError} is raised. |
| 552 | Otherwise, the argument may be a plain or |
| 553 | long integer or a floating point number. Conversion of floating |
Tim Peters | 7321ec4 | 2001-07-26 20:02:17 +0000 | [diff] [blame] | 554 | point numbers to integers truncates (towards zero). |
Walter Dörwald | f171540 | 2002-11-19 20:49:15 +0000 | [diff] [blame] | 555 | If the argument is outside the integer range a long object will |
| 556 | be returned instead. |
Fred Drake | 1e862e8 | 2000-02-17 17:45:52 +0000 | [diff] [blame] | 557 | \end{funcdesc} |
| 558 | |
Guido van Rossum | 3978d75 | 1997-03-03 16:03:27 +0000 | [diff] [blame] | 559 | \begin{funcdesc}{intern}{string} |
| 560 | Enter \var{string} in the table of ``interned'' strings and return |
| 561 | the interned string -- which is \var{string} itself or a copy. |
| 562 | Interning strings is useful to gain a little performance on |
| 563 | dictionary lookup -- if the keys in a dictionary are interned, and |
| 564 | the lookup key is interned, the key comparisons (after hashing) can |
| 565 | be done by a pointer compare instead of a string compare. Normally, |
| 566 | the names used in Python programs are automatically interned, and |
| 567 | the dictionaries used to hold module, class or instance attributes |
Guido van Rossum | 45ec02a | 2002-08-19 21:43:18 +0000 | [diff] [blame] | 568 | have interned keys. \versionchanged[Interned strings are not |
| 569 | immortal (like they used to be in Python 2.2 and before); |
| 570 | you must keep a reference to the return value of \function{intern()} |
| 571 | around to benefit from it]{2.3} |
Guido van Rossum | 3978d75 | 1997-03-03 16:03:27 +0000 | [diff] [blame] | 572 | \end{funcdesc} |
| 573 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 574 | \begin{funcdesc}{isinstance}{object, classinfo} |
| 575 | Return true if the \var{object} argument is an instance of the |
| 576 | \var{classinfo} argument, or of a (direct or indirect) subclass |
| 577 | thereof. Also return true if \var{classinfo} is a type object and |
| 578 | \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] | 579 | class instance or an object of the given type, the function always |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 580 | returns false. If \var{classinfo} is neither a class object nor a |
| 581 | type object, it may be a tuple of class or type objects, or may |
| 582 | recursively contain other such tuples (other sequence types are not |
| 583 | accepted). If \var{classinfo} is not a class, type, or tuple of |
| 584 | classes, types, and such tuples, a \exception{TypeError} exception |
| 585 | is raised. |
| 586 | \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] | 587 | \end{funcdesc} |
| 588 | |
Walter Dörwald | d9a6ad3 | 2002-12-12 16:41:44 +0000 | [diff] [blame] | 589 | \begin{funcdesc}{issubclass}{class, classinfo} |
| 590 | Return true if \var{class} is a subclass (direct or indirect) of |
| 591 | \var{classinfo}. A class is considered a subclass of itself. |
| 592 | \var{classinfo} may be a tuple of class objects, in which case every |
| 593 | entry in \var{classinfo} will be checked. In any other case, a |
| 594 | \exception{TypeError} exception is raised. |
| 595 | \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] | 596 | \end{funcdesc} |
| 597 | |
Fred Drake | 00bb329 | 2001-09-06 19:04:29 +0000 | [diff] [blame] | 598 | \begin{funcdesc}{iter}{o\optional{, sentinel}} |
| 599 | Return an iterator object. The first argument is interpreted very |
| 600 | differently depending on the presence of the second argument. |
| 601 | Without a second argument, \var{o} must be a collection object which |
| 602 | supports the iteration protocol (the \method{__iter__()} method), or |
| 603 | it must support the sequence protocol (the \method{__getitem__()} |
| 604 | method with integer arguments starting at \code{0}). If it does not |
| 605 | support either of those protocols, \exception{TypeError} is raised. |
| 606 | If the second argument, \var{sentinel}, is given, then \var{o} must |
| 607 | be a callable object. The iterator created in this case will call |
| 608 | \var{o} with no arguments for each call to its \method{next()} |
| 609 | method; if the value returned is equal to \var{sentinel}, |
| 610 | \exception{StopIteration} will be raised, otherwise the value will |
| 611 | be returned. |
| 612 | \versionadded{2.2} |
| 613 | \end{funcdesc} |
| 614 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 615 | \begin{funcdesc}{len}{s} |
| 616 | Return the length (the number of items) of an object. The argument |
| 617 | may be a sequence (string, tuple or list) or a mapping (dictionary). |
| 618 | \end{funcdesc} |
| 619 | |
Tim Peters | 1fc240e | 2001-10-26 05:06:50 +0000 | [diff] [blame] | 620 | \begin{funcdesc}{list}{\optional{sequence}} |
Fred Drake | eacdec6 | 2001-05-02 20:19:19 +0000 | [diff] [blame] | 621 | Return a list whose items are the same and in the same order as |
| 622 | \var{sequence}'s items. \var{sequence} may be either a sequence, a |
| 623 | container that supports iteration, or an iterator object. If |
| 624 | \var{sequence} is already a list, a copy is made and returned, |
| 625 | similar to \code{\var{sequence}[:]}. For instance, |
| 626 | \code{list('abc')} returns \code{['a', 'b', 'c']} and \code{list( |
| 627 | (1, 2, 3) )} returns \code{[1, 2, 3]}. |
Guido van Rossum | 921f32c | 1997-06-02 17:21:20 +0000 | [diff] [blame] | 628 | \end{funcdesc} |
| 629 | |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 630 | \begin{funcdesc}{locals}{} |
Raymond Hettinger | 69bf8f3 | 2003-01-04 02:16:22 +0000 | [diff] [blame] | 631 | Update and return a dictionary representing the current local symbol table. |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 632 | \warning{The contents of this dictionary should not be modified; |
| 633 | changes may not affect the values of local variables used by the |
| 634 | interpreter.} |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 635 | \end{funcdesc} |
| 636 | |
Fred Drake | 17383b9 | 2000-11-17 19:44:14 +0000 | [diff] [blame] | 637 | \begin{funcdesc}{long}{x\optional{, radix}} |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 638 | 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] | 639 | string, it must contain a possibly signed number of |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 640 | arbitrary size, possibly embedded in whitespace; |
Fred Drake | 17383b9 | 2000-11-17 19:44:14 +0000 | [diff] [blame] | 641 | this behaves identical to \code{string.atol(\var{x})}. The |
| 642 | \var{radix} argument is interpreted in the same way as for |
| 643 | \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] | 644 | Otherwise, the argument may be a plain or |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 645 | 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] | 646 | the same value is returned. Conversion of floating |
Tim Peters | 1c33daf | 2001-09-30 06:18:26 +0000 | [diff] [blame] | 647 | point numbers to integers truncates (towards zero). |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 648 | \end{funcdesc} |
| 649 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 650 | \begin{funcdesc}{map}{function, list, ...} |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 651 | Apply \var{function} to every item of \var{list} and return a list |
| 652 | of the results. If additional \var{list} arguments are passed, |
| 653 | \var{function} must take that many arguments and is applied to the |
| 654 | items of all lists in parallel; if a list is shorter than another it |
| 655 | is assumed to be extended with \code{None} items. If \var{function} |
| 656 | is \code{None}, the identity function is assumed; if there are |
| 657 | multiple list arguments, \function{map()} returns a list consisting |
| 658 | of tuples containing the corresponding items from all lists (a kind |
| 659 | of transpose operation). The \var{list} arguments may be any kind |
| 660 | of sequence; the result is always a list. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 661 | \end{funcdesc} |
| 662 | |
Guido van Rossum | 5eabf38 | 1998-11-25 18:53:05 +0000 | [diff] [blame] | 663 | \begin{funcdesc}{max}{s\optional{, args...}} |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 664 | With a single argument \var{s}, return the largest item of a |
| 665 | non-empty sequence (such as a string, tuple or list). With more |
| 666 | than one argument, return the largest of the arguments. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 667 | \end{funcdesc} |
| 668 | |
Guido van Rossum | 5eabf38 | 1998-11-25 18:53:05 +0000 | [diff] [blame] | 669 | \begin{funcdesc}{min}{s\optional{, args...}} |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 670 | With a single argument \var{s}, return the smallest item of a |
| 671 | non-empty sequence (such as a string, tuple or list). With more |
| 672 | than one argument, return the smallest of the arguments. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 673 | \end{funcdesc} |
| 674 | |
| 675 | \begin{funcdesc}{oct}{x} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 676 | Convert an integer number (of any size) to an octal string. The |
Fred Drake | 91f2f26 | 2001-07-06 19:28:48 +0000 | [diff] [blame] | 677 | result is a valid Python expression. Note: this always yields an |
| 678 | unsigned literal. For example, on a 32-bit machine, \code{oct(-1)} |
| 679 | yields \code{'037777777777'}. When evaluated on a machine with the |
| 680 | 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] | 681 | 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] | 682 | \exception{OverflowError} exception. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 683 | \end{funcdesc} |
| 684 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 685 | \begin{funcdesc}{open}{filename\optional{, mode\optional{, bufsize}}} |
Tim Peters | 2e29bfb | 2001-09-20 19:55:29 +0000 | [diff] [blame] | 686 | An alias for the \function{file()} function above. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 687 | \end{funcdesc} |
| 688 | |
| 689 | \begin{funcdesc}{ord}{c} |
Fred Drake | 33d5184 | 2000-04-06 14:43:12 +0000 | [diff] [blame] | 690 | Return the \ASCII{} value of a string of one character or a Unicode |
| 691 | character. E.g., \code{ord('a')} returns the integer \code{97}, |
| 692 | \code{ord(u'\\u2020')} returns \code{8224}. This is the inverse of |
| 693 | \function{chr()} for strings and of \function{unichr()} for Unicode |
| 694 | characters. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 695 | \end{funcdesc} |
| 696 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 697 | \begin{funcdesc}{pow}{x, y\optional{, z}} |
Guido van Rossum | b8b264b | 1994-08-12 13:13:50 +0000 | [diff] [blame] | 698 | Return \var{x} to the power \var{y}; if \var{z} is present, return |
| 699 | \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] | 700 | efficiently than \code{pow(\var{x}, \var{y}) \%\ \var{z}}). The |
| 701 | arguments must have numeric types. With mixed operand types, the |
| 702 | coercion rules for binary arithmetic operators apply. For int and |
| 703 | long int operands, the result has the same type as the operands |
| 704 | (after coercion) unless the second argument is negative; in that |
| 705 | case, all arguments are converted to float and a float result is |
| 706 | delivered. For example, \code{10**2} returns \code{100}, but |
| 707 | \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] | 708 | Python 2.2. In Python 2.1 and before, if both arguments were of integer |
| 709 | types and the second argument was negative, an exception was raised.) |
Tim Peters | 2e29bfb | 2001-09-20 19:55:29 +0000 | [diff] [blame] | 710 | If the second argument is negative, the third argument must be omitted. |
Tim Peters | 32f453e | 2001-09-03 08:35:41 +0000 | [diff] [blame] | 711 | If \var{z} is present, \var{x} and \var{y} must be of integer types, |
| 712 | and \var{y} must be non-negative. (This restriction was added in |
| 713 | Python 2.2. In Python 2.1 and before, floating 3-argument \code{pow()} |
| 714 | returned platform-dependent results depending on floating-point |
| 715 | rounding accidents.) |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 716 | \end{funcdesc} |
| 717 | |
Fred Drake | 8f53cdc | 2003-05-10 19:46:39 +0000 | [diff] [blame] | 718 | \begin{funcdesc}{property}{\optional{fget\optional{, fset\optional{, |
| 719 | fdel\optional{, doc}}}}} |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 720 | Return a property attribute for new-style classes (classes that |
Fred Drake | 8f53cdc | 2003-05-10 19:46:39 +0000 | [diff] [blame] | 721 | derive from \class{object}). |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 722 | |
| 723 | \var{fget} is a function for getting an attribute value, likewise |
| 724 | \var{fset} is a function for setting, and \var{fdel} a function |
| 725 | for del'ing, an attribute. Typical use is to define a managed attribute x: |
| 726 | |
| 727 | \begin{verbatim} |
| 728 | class C(object): |
| 729 | def getx(self): return self.__x |
| 730 | def setx(self, value): self.__x = value |
| 731 | def delx(self): del self.__x |
| 732 | x = property(getx, setx, delx, "I'm the 'x' property.") |
| 733 | \end{verbatim} |
| 734 | |
| 735 | \versionadded{2.2} |
| 736 | \end{funcdesc} |
| 737 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 738 | \begin{funcdesc}{range}{\optional{start,} stop\optional{, step}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 739 | This is a versatile function to create lists containing arithmetic |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 740 | progressions. It is most often used in \keyword{for} loops. The |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 741 | arguments must be plain integers. If the \var{step} argument is |
| 742 | omitted, it defaults to \code{1}. If the \var{start} argument is |
| 743 | omitted, it defaults to \code{0}. The full form returns a list of |
| 744 | plain integers \code{[\var{start}, \var{start} + \var{step}, |
| 745 | \var{start} + 2 * \var{step}, \ldots]}. If \var{step} is positive, |
| 746 | the last element is the largest \code{\var{start} + \var{i} * |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 747 | \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] | 748 | element is the largest \code{\var{start} + \var{i} * \var{step}} |
Fred Drake | 6251c16 | 1998-04-03 07:15:54 +0000 | [diff] [blame] | 749 | greater than \var{stop}. \var{step} must not be zero (or else |
| 750 | \exception{ValueError} is raised). Example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 751 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 752 | \begin{verbatim} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 753 | >>> range(10) |
| 754 | [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] |
| 755 | >>> range(1, 11) |
| 756 | [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] |
| 757 | >>> range(0, 30, 5) |
| 758 | [0, 5, 10, 15, 20, 25] |
| 759 | >>> range(0, 10, 3) |
| 760 | [0, 3, 6, 9] |
| 761 | >>> range(0, -10, -1) |
| 762 | [0, -1, -2, -3, -4, -5, -6, -7, -8, -9] |
| 763 | >>> range(0) |
| 764 | [] |
| 765 | >>> range(1, 0) |
| 766 | [] |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 767 | \end{verbatim} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 768 | \end{funcdesc} |
| 769 | |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 770 | \begin{funcdesc}{raw_input}{\optional{prompt}} |
| 771 | If the \var{prompt} argument is present, it is written to standard output |
| 772 | without a trailing newline. The function then reads a line from input, |
| 773 | converts it to a string (stripping a trailing newline), and returns that. |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 774 | When \EOF{} is read, \exception{EOFError} is raised. Example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 775 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 776 | \begin{verbatim} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 777 | >>> s = raw_input('--> ') |
| 778 | --> Monty Python's Flying Circus |
| 779 | >>> s |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 780 | "Monty Python's Flying Circus" |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 781 | \end{verbatim} |
Guido van Rossum | 921f32c | 1997-06-02 17:21:20 +0000 | [diff] [blame] | 782 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 783 | If the \refmodule{readline} module was loaded, then |
| 784 | \function{raw_input()} will use it to provide elaborate |
| 785 | line editing and history features. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 786 | \end{funcdesc} |
| 787 | |
Guido van Rossum | 87e611e | 1999-01-06 23:10:51 +0000 | [diff] [blame] | 788 | \begin{funcdesc}{reduce}{function, sequence\optional{, initializer}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 789 | Apply \var{function} of two arguments cumulatively to the items of |
| 790 | \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] | 791 | a single value. For example, \code{reduce(lambda x, y: x+y, [1, 2, |
| 792 | 3, 4, 5])} calculates \code{((((1+2)+3)+4)+5)}. If the optional |
| 793 | \var{initializer} is present, it is placed before the items of the |
| 794 | sequence in the calculation, and serves as a default when the |
| 795 | sequence is empty. If \var{initializer} is not given and |
| 796 | \var{sequence} contains only one item, the first item is returned. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 797 | \end{funcdesc} |
| 798 | |
| 799 | \begin{funcdesc}{reload}{module} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 800 | Re-parse and re-initialize an already imported \var{module}. The |
| 801 | argument must be a module object, so it must have been successfully |
| 802 | imported before. This is useful if you have edited the module |
| 803 | source file using an external editor and want to try out the new |
| 804 | version without leaving the Python interpreter. The return value is |
| 805 | the module object (the same as the \var{module} argument). |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 806 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 807 | There are a number of caveats: |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 808 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 809 | If a module is syntactically correct but its initialization fails, |
| 810 | the first \keyword{import} statement for it does not bind its name |
| 811 | locally, but does store a (partially initialized) module object in |
| 812 | \code{sys.modules}. To reload the module you must first |
| 813 | \keyword{import} it again (this will bind the name to the partially |
| 814 | initialized module object) before you can \function{reload()} it. |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 815 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 816 | When a module is reloaded, its dictionary (containing the module's |
| 817 | global variables) is retained. Redefinitions of names will override |
| 818 | the old definitions, so this is generally not a problem. If the new |
| 819 | version of a module does not define a name that was defined by the |
| 820 | old version, the old definition remains. This feature can be used |
| 821 | to the module's advantage if it maintains a global table or cache of |
| 822 | objects --- with a \keyword{try} statement it can test for the |
| 823 | table's presence and skip its initialization if desired. |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 824 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 825 | It is legal though generally not very useful to reload built-in or |
| 826 | dynamically loaded modules, except for \refmodule{sys}, |
| 827 | \refmodule[main]{__main__} and \refmodule[builtin]{__builtin__}. In |
| 828 | many cases, however, extension modules are not designed to be |
| 829 | initialized more than once, and may fail in arbitrary ways when |
| 830 | reloaded. |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 831 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 832 | If a module imports objects from another module using \keyword{from} |
| 833 | \ldots{} \keyword{import} \ldots{}, calling \function{reload()} for |
| 834 | the other module does not redefine the objects imported from it --- |
| 835 | one way around this is to re-execute the \keyword{from} statement, |
| 836 | another is to use \keyword{import} and qualified names |
| 837 | (\var{module}.\var{name}) instead. |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 838 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 839 | If a module instantiates instances of a class, reloading the module |
| 840 | that defines the class does not affect the method definitions of the |
| 841 | instances --- they continue to use the old class definition. The |
| 842 | same is true for derived classes. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 843 | \end{funcdesc} |
| 844 | |
| 845 | \begin{funcdesc}{repr}{object} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 846 | Return a string containing a printable representation of an object. |
| 847 | This is the same value yielded by conversions (reverse quotes). |
| 848 | It is sometimes useful to be able to access this operation as an |
| 849 | ordinary function. For many types, this function makes an attempt |
| 850 | to return a string that would yield an object with the same value |
| 851 | when passed to \function{eval()}. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 852 | \end{funcdesc} |
| 853 | |
Fred Drake | 607f802 | 1998-08-24 20:30:07 +0000 | [diff] [blame] | 854 | \begin{funcdesc}{round}{x\optional{, n}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 855 | Return the floating point value \var{x} rounded to \var{n} digits |
| 856 | after the decimal point. If \var{n} is omitted, it defaults to zero. |
| 857 | The result is a floating point number. Values are rounded to the |
| 858 | 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] | 859 | 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] | 860 | \code{round(0.5)} is \code{1.0} and \code{round(-0.5)} is \code{-1.0}). |
| 861 | \end{funcdesc} |
| 862 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 863 | \begin{funcdesc}{setattr}{object, name, value} |
Fred Drake | 5352537 | 1998-03-03 21:56:15 +0000 | [diff] [blame] | 864 | This is the counterpart of \function{getattr()}. The arguments are an |
Fred Drake | 607f802 | 1998-08-24 20:30:07 +0000 | [diff] [blame] | 865 | object, a string and an arbitrary value. The string may name an |
| 866 | existing attribute or a new attribute. The function assigns the |
| 867 | value to the attribute, provided the object allows it. For example, |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 868 | \code{setattr(\var{x}, '\var{foobar}', 123)} is equivalent to |
| 869 | \code{\var{x}.\var{foobar} = 123}. |
| 870 | \end{funcdesc} |
| 871 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 872 | \begin{funcdesc}{slice}{\optional{start,} stop\optional{, step}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 873 | Return a slice object representing the set of indices specified by |
| 874 | \code{range(\var{start}, \var{stop}, \var{step})}. The \var{start} |
| 875 | and \var{step} arguments default to None. Slice objects have |
| 876 | read-only data attributes \member{start}, \member{stop} and |
| 877 | \member{step} which merely return the argument values (or their |
| 878 | default). They have no other explicit functionality; however they |
| 879 | are used by Numerical Python\index{Numerical Python} and other third |
| 880 | party extensions. Slice objects are also generated when extended |
| 881 | indexing syntax is used. For example: \samp{a[start:stop:step]} or |
| 882 | \samp{a[start:stop, i]}. |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 883 | \end{funcdesc} |
| 884 | |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 885 | \begin{funcdesc}{staticmethod}{function} |
| 886 | Return a static method for \var{function}. |
| 887 | |
| 888 | A static method does not receive an implicit first argument. |
| 889 | To declare a static method, use this idiom: |
| 890 | |
| 891 | \begin{verbatim} |
| 892 | class C: |
| 893 | def f(arg1, arg2, ...): ... |
| 894 | f = staticmethod(f) |
| 895 | \end{verbatim} |
| 896 | |
| 897 | It can be called either on the class (e.g. C.f()) or on an instance |
| 898 | (e.g. C().f()). The instance is ignored except for its class. |
| 899 | |
| 900 | Static methods in Python are similar to those found in Java or C++. |
| 901 | For a more advanced concept, see \ref{classmethod}. |
| 902 | \versionadded{2.2} |
| 903 | \end{funcdesc} |
| 904 | |
Fred Drake | 282be3a | 2003-04-22 14:52:08 +0000 | [diff] [blame] | 905 | \begin{funcdesc}{sum}{sequence\optional{, start}} |
| 906 | Sums \var{start} and the items of a \var{sequence}, from left to |
| 907 | right, and returns the total. \var{start} defaults to \code{0}. |
| 908 | The \var{sequence}'s items are normally numbers, and are not allowed |
| 909 | to be strings. The fast, correct way to concatenate sequence of |
| 910 | strings is by calling \code{''.join(\var{sequence})}. |
Martin v. Löwis | 7472336 | 2003-05-31 08:02:38 +0000 | [diff] [blame^] | 911 | Note that \code{sum(range(n), m)} equals \code{reduce(operator.add, range(n), m)} |
Alex Martelli | a70b191 | 2003-04-22 08:12:33 +0000 | [diff] [blame] | 912 | \versionadded{2.3} |
| 913 | \end{funcdesc} |
| 914 | |
Neal Norwitz | e9ce25e | 2002-12-17 01:02:57 +0000 | [diff] [blame] | 915 | \begin{funcdesc}{super}{type\optional{object-or-type}} |
| 916 | Return the superclass of \var{type}. If the second argument is omitted |
| 917 | the super object returned is unbound. If the second argument is an |
| 918 | object, isinstance(obj, type) must be true. If the second argument is a |
| 919 | type, issubclass(type2, type) must be true. |
| 920 | |
| 921 | A typical use for calling a cooperative superclass method is: |
| 922 | \begin{verbatim} |
| 923 | class C(B): |
| 924 | def meth(self, arg): |
| 925 | super(C, self).meth(arg) |
| 926 | \end{verbatim} |
| 927 | \versionadded{2.2} |
| 928 | \end{funcdesc} |
| 929 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 930 | \begin{funcdesc}{str}{object} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 931 | Return a string containing a nicely printable representation of an |
| 932 | object. For strings, this returns the string itself. The |
| 933 | difference with \code{repr(\var{object})} is that |
| 934 | \code{str(\var{object})} does not always attempt to return a string |
| 935 | that is acceptable to \function{eval()}; its goal is to return a |
| 936 | printable string. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 937 | \end{funcdesc} |
| 938 | |
Tim Peters | 1fc240e | 2001-10-26 05:06:50 +0000 | [diff] [blame] | 939 | \begin{funcdesc}{tuple}{\optional{sequence}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 940 | Return a tuple whose items are the same and in the same order as |
| 941 | \var{sequence}'s items. \var{sequence} may be a sequence, a |
| 942 | container that supports iteration, or an iterator object. |
| 943 | If \var{sequence} is already a tuple, it |
| 944 | is returned unchanged. For instance, \code{tuple('abc')} returns |
| 945 | returns \code{('a', 'b', 'c')} and \code{tuple([1, 2, 3])} returns |
| 946 | \code{(1, 2, 3)}. |
Guido van Rossum | b8b264b | 1994-08-12 13:13:50 +0000 | [diff] [blame] | 947 | \end{funcdesc} |
| 948 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 949 | \begin{funcdesc}{type}{object} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 950 | Return the type of an \var{object}. The return value is a |
| 951 | type\obindex{type} object. The standard module |
| 952 | \module{types}\refstmodindex{types} defines names for all built-in |
Fred Drake | 9482d25 | 2002-11-01 21:33:44 +0000 | [diff] [blame] | 953 | types that don't already have built-in names. |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 954 | For instance: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 955 | |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 956 | \begin{verbatim} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 957 | >>> import types |
Fred Drake | 9482d25 | 2002-11-01 21:33:44 +0000 | [diff] [blame] | 958 | >>> x = 'abc' |
| 959 | >>> if type(x) is str: print "It's a string" |
| 960 | ... |
| 961 | It's a string |
| 962 | >>> def f(): pass |
| 963 | ... |
| 964 | >>> if type(f) is types.FunctionType: print "It's a function" |
| 965 | ... |
| 966 | It's a function |
Fred Drake | 1947991 | 1998-02-13 06:58:54 +0000 | [diff] [blame] | 967 | \end{verbatim} |
Fred Drake | 9482d25 | 2002-11-01 21:33:44 +0000 | [diff] [blame] | 968 | |
| 969 | The \function{isinstance()} built-in function is recommended for |
| 970 | testing the type of an object. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 971 | \end{funcdesc} |
Guido van Rossum | 68cfbe7 | 1994-02-24 11:28:27 +0000 | [diff] [blame] | 972 | |
Fred Drake | 33d5184 | 2000-04-06 14:43:12 +0000 | [diff] [blame] | 973 | \begin{funcdesc}{unichr}{i} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 974 | Return the Unicode string of one character whose Unicode code is the |
| 975 | integer \var{i}. For example, \code{unichr(97)} returns the string |
| 976 | \code{u'a'}. This is the inverse of \function{ord()} for Unicode |
| 977 | strings. The argument must be in the range [0..65535], inclusive. |
| 978 | \exception{ValueError} is raised otherwise. |
| 979 | \versionadded{2.0} |
Fred Drake | 33d5184 | 2000-04-06 14:43:12 +0000 | [diff] [blame] | 980 | \end{funcdesc} |
| 981 | |
Marc-André Lemburg | b5507ec | 2001-10-19 12:02:29 +0000 | [diff] [blame] | 982 | \begin{funcdesc}{unicode}{object\optional{, encoding\optional{, errors}}} |
| 983 | Return the Unicode string version of \var{object} using one of the |
| 984 | following modes: |
| 985 | |
| 986 | If \var{encoding} and/or \var{errors} are given, \code{unicode()} |
| 987 | will decode the object which can either be an 8-bit string or a |
| 988 | character buffer using the codec for \var{encoding}. The |
Fred Drake | 4254cbd | 2002-07-09 05:25:46 +0000 | [diff] [blame] | 989 | \var{encoding} parameter is a string giving the name of an encoding; |
| 990 | if the encoding is not known, \exception{LookupError} is raised. |
Marc-André Lemburg | b5507ec | 2001-10-19 12:02:29 +0000 | [diff] [blame] | 991 | Error handling is done according to \var{errors}; this specifies the |
| 992 | treatment of characters which are invalid in the input encoding. If |
| 993 | \var{errors} is \code{'strict'} (the default), a |
| 994 | \exception{ValueError} is raised on errors, while a value of |
| 995 | \code{'ignore'} causes errors to be silently ignored, and a value of |
| 996 | \code{'replace'} causes the official Unicode replacement character, |
| 997 | \code{U+FFFD}, to be used to replace input characters which cannot |
| 998 | be decoded. See also the \refmodule{codecs} module. |
| 999 | |
| 1000 | If no optional parameters are given, \code{unicode()} will mimic the |
| 1001 | behaviour of \code{str()} except that it returns Unicode strings |
Fred Drake | 50e1286 | 2002-07-08 14:29:05 +0000 | [diff] [blame] | 1002 | instead of 8-bit strings. More precisely, if \var{object} is a |
| 1003 | Unicode string or subclass it will return that Unicode string without |
Fred Drake | 78e057a | 2002-06-29 16:06:47 +0000 | [diff] [blame] | 1004 | any additional decoding applied. |
| 1005 | |
| 1006 | For objects which provide a \method{__unicode__()} method, it will |
| 1007 | call this method without arguments to create a Unicode string. For |
| 1008 | all other objects, the 8-bit string version or representation is |
| 1009 | requested and then converted to a Unicode string using the codec for |
| 1010 | the default encoding in \code{'strict'} mode. |
| 1011 | |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 1012 | \versionadded{2.0} |
Fred Drake | 78e057a | 2002-06-29 16:06:47 +0000 | [diff] [blame] | 1013 | \versionchanged[Support for \method{__unicode__()} added]{2.2} |
Fred Drake | 33d5184 | 2000-04-06 14:43:12 +0000 | [diff] [blame] | 1014 | \end{funcdesc} |
| 1015 | |
Guido van Rossum | 6bb1adc | 1995-03-13 10:03:32 +0000 | [diff] [blame] | 1016 | \begin{funcdesc}{vars}{\optional{object}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 1017 | Without arguments, return a dictionary corresponding to the current |
| 1018 | local symbol table. With a module, class or class instance object |
| 1019 | as argument (or anything else that has a \member{__dict__} |
| 1020 | attribute), returns a dictionary corresponding to the object's |
| 1021 | symbol table. The returned dictionary should not be modified: the |
| 1022 | effects on the corresponding symbol table are undefined.\footnote{ |
| 1023 | In the current implementation, local variable bindings cannot |
| 1024 | normally be affected this way, but variables retrieved from |
| 1025 | other scopes (such as modules) can be. This may change.} |
Guido van Rossum | 1738311 | 1994-04-21 10:32:28 +0000 | [diff] [blame] | 1026 | \end{funcdesc} |
| 1027 | |
Fred Drake | cce1090 | 1998-03-17 06:33:25 +0000 | [diff] [blame] | 1028 | \begin{funcdesc}{xrange}{\optional{start,} stop\optional{, step}} |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 1029 | This function is very similar to \function{range()}, but returns an |
| 1030 | ``xrange object'' instead of a list. This is an opaque sequence |
| 1031 | type which yields the same values as the corresponding list, without |
| 1032 | actually storing them all simultaneously. The advantage of |
| 1033 | \function{xrange()} over \function{range()} is minimal (since |
| 1034 | \function{xrange()} still has to create the values when asked for |
| 1035 | them) except when a very large range is used on a memory-starved |
| 1036 | machine or when all of the range's elements are never used (such as |
| 1037 | when the loop is usually terminated with \keyword{break}). |
Guido van Rossum | 68cfbe7 | 1994-02-24 11:28:27 +0000 | [diff] [blame] | 1038 | \end{funcdesc} |
Barry Warsaw | faefa2a | 2000-08-03 15:46:17 +0000 | [diff] [blame] | 1039 | |
Fred Drake | 8b168ba | 2000-08-03 17:29:13 +0000 | [diff] [blame] | 1040 | \begin{funcdesc}{zip}{seq1, \moreargs} |
Fred Drake | 5172adc | 2001-12-03 18:35:05 +0000 | [diff] [blame] | 1041 | This function returns a list of tuples, where the \var{i}-th tuple contains |
Fred Drake | e0063d2 | 2001-10-09 19:31:08 +0000 | [diff] [blame] | 1042 | the \var{i}-th element from each of the argument sequences. At |
| 1043 | least one sequence is required, otherwise a \exception{TypeError} is |
| 1044 | raised. The returned list is truncated in length to the length of |
| 1045 | the shortest argument sequence. When there are multiple argument |
| 1046 | sequences which are all of the same length, \function{zip()} is |
| 1047 | similar to \function{map()} with an initial argument of \code{None}. |
| 1048 | With a single sequence argument, it returns a list of 1-tuples. |
| 1049 | \versionadded{2.0} |
Fred Drake | 8b168ba | 2000-08-03 17:29:13 +0000 | [diff] [blame] | 1050 | \end{funcdesc} |