Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 1 | \section{Built-in Functions} |
Fred Drake | 90f2e5e | 1997-12-16 04:06:33 +0000 | [diff] [blame] | 2 | \label{built-in-funcs} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 3 | |
| 4 | The Python interpreter has a number of functions built into it that |
| 5 | are always available. They are listed here in alphabetical order. |
| 6 | |
| 7 | |
| 8 | \renewcommand{\indexsubitem}{(built-in function)} |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 9 | |
| 10 | \begin{funcdesc}{__import__}{name\optional{, globals\optional{, locals\optional{, fromlist}}}} |
| 11 | This function is invoked by the \code{import} statement. It |
| 12 | mainly exists so that you can replace it with another |
| 13 | function that has a compatible interface, in order to change the |
| 14 | semantics of the \code{import} statement. For examples of why and |
| 15 | how you would do this, see the standard library modules \code{ni}, |
| 16 | \code{ihooks} and \code{rexec}. See also the built-in module |
| 17 | \code{imp}, which defines some useful operations out of which you can |
Fred Drake | e14388c | 1997-12-15 22:28:38 +0000 | [diff] [blame] | 18 | build your own \code{__import__()} function. |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 19 | \stindex{import} |
Fred Drake | e14388c | 1997-12-15 22:28:38 +0000 | [diff] [blame] | 20 | \refstmodindex{ni} |
| 21 | \refstmodindex{ihooks} |
| 22 | \refstmodindex{rexec} |
| 23 | \refbimodindex{imp} |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 24 | |
| 25 | For example, the statement \code{import spam} results in the following |
| 26 | call: |
| 27 | \code{__import__('spam', globals(), locals(), [])}; |
| 28 | the statement \code{from spam.ham import eggs} results in |
| 29 | \code{__import__('spam.ham', globals(), locals(), ['eggs'])}. |
| 30 | Note that even though \code{locals()} and \code{['eggs']} are passed |
| 31 | in as arguments, the \code{__import__()} function does not set the |
| 32 | local variable named \code{eggs}; this is done by subsequent code that |
| 33 | is generated for the import statement. (In fact, the standard |
| 34 | implementation does not use its \var{locals} argument at all, and uses |
| 35 | its \var{globals} only to determine the package context of the |
| 36 | \code{import} statement.) |
| 37 | |
| 38 | When the \var{name} variable is of the form \code{package.module}, |
| 39 | normally, the top-level package (the name up till the first dot) is |
| 40 | returned, \emph{not} the module named by \var{name}. However, when a |
| 41 | non-empty \var{fromlist} argument is given, the module named by |
| 42 | \var{name} is returned. This is done for compatibility with the |
| 43 | bytecode generated for the different kinds of import statement; when |
| 44 | using \code{import spam.ham.eggs}, the top-level package \code{spam} |
| 45 | must be placed in the importing namespace, but when using \code{from |
| 46 | spam.ham import eggs}, the \code{spam.ham} subpackage must be used to |
| 47 | find the \code{eggs} variable. |
| 48 | \end{funcdesc} |
| 49 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 50 | \begin{funcdesc}{abs}{x} |
| 51 | 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] | 52 | 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] | 53 | complex number, its magnitude is returned. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 54 | \end{funcdesc} |
| 55 | |
Guido van Rossum | 0568d5e | 1995-10-08 01:06:46 +0000 | [diff] [blame] | 56 | \begin{funcdesc}{apply}{function\, args\optional{, keywords}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 57 | The \var{function} argument must be a callable object (a user-defined or |
| 58 | built-in function or method, or a class object) and the \var{args} |
| 59 | argument must be a tuple. The \var{function} is called with |
| 60 | \var{args} as argument list; the number of arguments is the the length |
| 61 | of the tuple. (This is different from just calling |
| 62 | \code{\var{func}(\var{args})}, since in that case there is always |
| 63 | exactly one argument.) |
Guido van Rossum | 0568d5e | 1995-10-08 01:06:46 +0000 | [diff] [blame] | 64 | If the optional \var{keywords} argument is present, it must be a |
| 65 | dictionary whose keys are strings. It specifies keyword arguments to |
| 66 | be added to the end of the the argument list. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 67 | \end{funcdesc} |
| 68 | |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 69 | \begin{funcdesc}{callable}{object} |
| 70 | Return true if the \var{object} argument appears callable, false if |
| 71 | not. If this returns true, it is still possible that a call fails, |
| 72 | but if it is false, calling \var{object} will never succeed. Note |
| 73 | that classes are callable (calling a class returns a new instance); |
| 74 | class instances are callable if they have an attribute \code{__call__}. |
| 75 | \end{funcdesc} |
| 76 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 77 | \begin{funcdesc}{chr}{i} |
| 78 | Return a string of one character whose \ASCII{} code is the integer |
| 79 | \var{i}, e.g., \code{chr(97)} returns the string \code{'a'}. This is the |
| 80 | inverse of \code{ord()}. The argument must be in the range [0..255], |
| 81 | inclusive. |
| 82 | \end{funcdesc} |
| 83 | |
| 84 | \begin{funcdesc}{cmp}{x\, y} |
| 85 | Compare the two objects \var{x} and \var{y} and return an integer |
| 86 | according to the outcome. The return value is negative if \code{\var{x} |
| 87 | < \var{y}}, zero if \code{\var{x} == \var{y}} and strictly positive if |
| 88 | \code{\var{x} > \var{y}}. |
| 89 | \end{funcdesc} |
| 90 | |
| 91 | \begin{funcdesc}{coerce}{x\, y} |
| 92 | Return a tuple consisting of the two numeric arguments converted to |
| 93 | a common type, using the same rules as used by arithmetic |
| 94 | operations. |
| 95 | \end{funcdesc} |
| 96 | |
| 97 | \begin{funcdesc}{compile}{string\, filename\, kind} |
| 98 | Compile the \var{string} into a code object. Code objects can be |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 99 | executed by an \code{exec} statement or evaluated by a call to |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 100 | \code{eval()}. The \var{filename} argument should |
| 101 | give the file from which the code was read; pass e.g. \code{'<string>'} |
| 102 | if it wasn't read from a file. The \var{kind} argument specifies |
| 103 | what kind of code must be compiled; it can be \code{'exec'} if |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 104 | \var{string} consists of a sequence of statements, \code{'eval'} |
| 105 | if it consists of a single expression, or \code{'single'} if |
| 106 | it consists of a single interactive statement (in the latter case, |
| 107 | expression statements that evaluate to something else than |
| 108 | \code{None} will printed). |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 109 | \end{funcdesc} |
| 110 | |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 111 | \begin{funcdesc}{complex}{real\optional{, imag}} |
| 112 | Create a complex number with the value \var{real} + \var{imag}*j. |
| 113 | Each argument may be any numeric type (including complex). |
| 114 | If \var{imag} is omitted, it defaults to zero and the function |
| 115 | serves as a numeric conversion function like \code{int}, \code{long} |
| 116 | and \code{float}. |
| 117 | \end{funcdesc} |
| 118 | |
Guido van Rossum | 1efbb0f | 1994-08-16 22:15:11 +0000 | [diff] [blame] | 119 | \begin{funcdesc}{delattr}{object\, name} |
| 120 | This is a relative of \code{setattr}. The arguments are an |
| 121 | object and a string. The string must be the name |
| 122 | of one of the object's attributes. The function deletes |
| 123 | the named attribute, provided the object allows it. For example, |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 124 | \code{delattr(\var{x}, '\var{foobar}')} is equivalent to |
Guido van Rossum | 1efbb0f | 1994-08-16 22:15:11 +0000 | [diff] [blame] | 125 | \code{del \var{x}.\var{foobar}}. |
| 126 | \end{funcdesc} |
| 127 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 128 | \begin{funcdesc}{dir}{} |
| 129 | Without arguments, return the list of names in the current local |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 130 | symbol table. With an argument, attempts to return a list of valid |
| 131 | attribute for that object. This information is gleaned from the |
| 132 | object's \code{__dict__}, \code{__methods__} and \code{__members__} |
| 133 | attributes, if defined. The list is not necessarily complete; e.g., |
| 134 | for classes, attributes defined in base classes are not included, |
| 135 | and for class instances, methods are not included. |
| 136 | The resulting list is sorted alphabetically. For example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 137 | |
| 138 | \bcode\begin{verbatim} |
| 139 | >>> import sys |
| 140 | >>> dir() |
| 141 | ['sys'] |
| 142 | >>> dir(sys) |
| 143 | ['argv', 'exit', 'modules', 'path', 'stderr', 'stdin', 'stdout'] |
| 144 | >>> |
| 145 | \end{verbatim}\ecode |
| 146 | \end{funcdesc} |
| 147 | |
| 148 | \begin{funcdesc}{divmod}{a\, b} |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 149 | Take two numbers as arguments and return a pair of numbers consisting |
| 150 | of their quotient and remainder when using long division. With mixed |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 151 | operand types, the rules for binary arithmetic operators apply. For |
| 152 | plain and long integers, the result is the same as |
| 153 | \code{(\var{a} / \var{b}, \var{a} \%{} \var{b})}. |
| 154 | For floating point numbers the result is the same as |
| 155 | \code{(math.floor(\var{a} / \var{b}), \var{a} \%{} \var{b})}. |
| 156 | \end{funcdesc} |
| 157 | |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 158 | \begin{funcdesc}{eval}{expression\optional{\, globals\optional{\, locals}}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 159 | The arguments are a string and two optional dictionaries. The |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 160 | \var{expression} argument is parsed and evaluated as a Python |
| 161 | expression (technically speaking, a condition list) using the |
| 162 | \var{globals} and \var{locals} dictionaries as global and local name |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 163 | space. If the \var{locals} dictionary is omitted it defaults to |
| 164 | the \var{globals} dictionary. If both dictionaries are omitted, the |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 165 | expression is executed in the environment where \code{eval} is |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 166 | called. The return value is the result of the evaluated expression. |
| 167 | Syntax errors are reported as exceptions. Example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 168 | |
| 169 | \bcode\begin{verbatim} |
| 170 | >>> x = 1 |
| 171 | >>> print eval('x+1') |
| 172 | 2 |
| 173 | >>> |
| 174 | \end{verbatim}\ecode |
Guido van Rossum | e47da0a | 1997-07-17 16:34:52 +0000 | [diff] [blame] | 175 | % |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 176 | This function can also be used to execute arbitrary code objects |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 177 | (e.g.\ created by \code{compile()}). In this case pass a code |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 178 | object instead of a string. The code object must have been compiled |
| 179 | passing \code{'eval'} to the \var{kind} argument. |
| 180 | |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 181 | Hints: dynamic execution of statements is supported by the |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 182 | \code{exec} statement. Execution of statements from a file is |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 183 | supported by the \code{execfile()} function. The \code{globals()} |
| 184 | and \code{locals()} functions returns the current global and local |
| 185 | dictionary, respectively, which may be useful |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 186 | to pass around for use by \code{eval()} or \code{execfile()}. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 187 | |
| 188 | \end{funcdesc} |
| 189 | |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 190 | \begin{funcdesc}{execfile}{file\optional{\, globals\optional{\, locals}}} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 191 | This function is similar to the |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 192 | \code{exec} statement, but parses a file instead of a string. It is |
| 193 | different from the \code{import} statement in that it does not use |
Guido van Rossum | 8675115 | 1995-02-28 17:14:32 +0000 | [diff] [blame] | 194 | the module administration --- it reads the file unconditionally and |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 195 | does not create a new module.\footnote{It is used relatively rarely |
| 196 | so does not warrant being made into a statement.} |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 197 | |
| 198 | The arguments are a file name and two optional dictionaries. The |
| 199 | file is parsed and evaluated as a sequence of Python statements |
| 200 | (similarly to a module) using the \var{globals} and \var{locals} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 201 | dictionaries as global and local name space. If the \var{locals} |
| 202 | dictionary is omitted it defaults to the \var{globals} dictionary. |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 203 | If both dictionaries are omitted, the expression is executed in the |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 204 | environment where \code{execfile()} is called. The return value is |
| 205 | \code{None}. |
Guido van Rossum | f860162 | 1995-01-10 10:50:24 +0000 | [diff] [blame] | 206 | \end{funcdesc} |
| 207 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 208 | \begin{funcdesc}{filter}{function\, list} |
| 209 | Construct a list from those elements of \var{list} for which |
| 210 | \var{function} returns true. If \var{list} is a string or a tuple, |
| 211 | the result also has that type; otherwise it is always a list. If |
| 212 | \var{function} is \code{None}, the identity function is assumed, |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 213 | i.e.\ all elements of \var{list} that are false (zero or empty) are |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 214 | removed. |
| 215 | \end{funcdesc} |
| 216 | |
| 217 | \begin{funcdesc}{float}{x} |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 218 | Convert a string or a number to floating point. If the argument is a |
| 219 | string, it must contain a possibly singed decimal or floating point |
| 220 | number, possibly embedded in whitespace; |
| 221 | this behaves identical to \code{string.atof(\var{x})}. |
| 222 | Otherwise, the argument may be a plain or |
| 223 | long integer or a floating point number, and a floating point number |
| 224 | with the same value (within Python's floating point precision) is |
| 225 | returned. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 226 | \end{funcdesc} |
| 227 | |
| 228 | \begin{funcdesc}{getattr}{object\, name} |
| 229 | The arguments are an object and a string. The string must be the |
| 230 | name |
| 231 | of one of the object's attributes. The result is the value of that |
| 232 | attribute. For example, \code{getattr(\var{x}, '\var{foobar}')} is equivalent to |
| 233 | \code{\var{x}.\var{foobar}}. |
| 234 | \end{funcdesc} |
| 235 | |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 236 | \begin{funcdesc}{globals}{} |
| 237 | Return a dictionary representing the current global symbol table. |
| 238 | This is always the dictionary of the current module (inside a |
| 239 | function or method, this is the module where it is defined, not the |
| 240 | module from which it is called). |
| 241 | \end{funcdesc} |
| 242 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 243 | \begin{funcdesc}{hasattr}{object\, name} |
| 244 | The arguments are an object and a string. The result is 1 if the |
| 245 | string is the name of one of the object's attributes, 0 if not. |
| 246 | (This is implemented by calling \code{getattr(object, name)} and |
| 247 | seeing whether it raises an exception or not.) |
| 248 | \end{funcdesc} |
| 249 | |
| 250 | \begin{funcdesc}{hash}{object} |
| 251 | 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] | 252 | are integers. They are used to quickly compare dictionary |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 253 | keys during a dictionary lookup. Numeric values that compare equal |
| 254 | have the same hash value (even if they are of different types, e.g. |
| 255 | 1 and 1.0). |
| 256 | \end{funcdesc} |
| 257 | |
| 258 | \begin{funcdesc}{hex}{x} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 259 | Convert an integer number (of any size) to a hexadecimal string. |
Guido van Rossum | 5cd7520 | 1997-01-14 18:44:23 +0000 | [diff] [blame] | 260 | The result is a valid Python expression. Note: this always yields |
| 261 | an unsigned literal, e.g. on a 32-bit machine, \code{hex(-1)} yields |
| 262 | \code{'0xffffffff'}. When evaluated on a machine with the same |
| 263 | word size, this literal is evaluated as -1; at a different word |
| 264 | size, it may turn up as a large positive number or raise an |
| 265 | \code{OverflowError} exception. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 266 | \end{funcdesc} |
| 267 | |
| 268 | \begin{funcdesc}{id}{object} |
| 269 | Return the `identity' of an object. This is an integer which is |
| 270 | guaranteed to be unique and constant for this object during its |
| 271 | lifetime. (Two objects whose lifetimes are disjunct may have the |
| 272 | same id() value.) (Implementation note: this is the address of the |
| 273 | object.) |
| 274 | \end{funcdesc} |
| 275 | |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 276 | \begin{funcdesc}{input}{\optional{prompt}} |
| 277 | Almost equivalent to \code{eval(raw_input(\var{prompt}))}. Like |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 278 | \code{raw_input()}, the \var{prompt} argument is optional, and the |
| 279 | \code{readline} module is used when loaded. The difference |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 280 | is that a long input expression may be broken over multiple lines using |
| 281 | the backslash convention. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 282 | \end{funcdesc} |
| 283 | |
Guido van Rossum | 3978d75 | 1997-03-03 16:03:27 +0000 | [diff] [blame] | 284 | \begin{funcdesc}{intern}{string} |
| 285 | Enter \var{string} in the table of ``interned'' strings and return |
| 286 | the interned string -- which is \var{string} itself or a copy. |
| 287 | Interning strings is useful to gain a little performance on |
| 288 | dictionary lookup -- if the keys in a dictionary are interned, and |
| 289 | the lookup key is interned, the key comparisons (after hashing) can |
| 290 | be done by a pointer compare instead of a string compare. Normally, |
| 291 | the names used in Python programs are automatically interned, and |
| 292 | the dictionaries used to hold module, class or instance attributes |
| 293 | have interned keys. Interned strings are immortal (i.e. never get |
| 294 | garbage collected). |
| 295 | \end{funcdesc} |
| 296 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 297 | \begin{funcdesc}{int}{x} |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 298 | Convert a string or number to a plain integer. If the argument is a |
| 299 | string, it must contain a possibly singed decimal number |
| 300 | representable as a Python integer, possibly embedded in whitespace; |
| 301 | this behaves identical to \code{string.atoi(\var{x})}. |
| 302 | Otherwise, the argument may be a plain or |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 303 | long integer or a floating point number. Conversion of floating |
| 304 | point numbers to integers is defined by the C semantics; normally |
Guido van Rossum | ecde781 | 1995-03-28 13:35:14 +0000 | [diff] [blame] | 305 | the conversion truncates towards zero.\footnote{This is ugly --- the |
| 306 | language definition should require truncation towards zero.} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 307 | \end{funcdesc} |
| 308 | |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 309 | \begin{funcdesc}{isinstance}{object, class} |
| 310 | Return true if the \var{object} argument is an instance of the |
| 311 | \var{class} argument, or of a (direct or indirect) subclass thereof. |
Guido van Rossum | 3593e5c | 1997-12-02 19:15:01 +0000 | [diff] [blame] | 312 | Also return true if \var{class} is a type object and \var{object} is |
| 313 | an object of that type. If \var{object} is not a class instance or a |
| 314 | object of the given type, the function always returns false. If |
| 315 | \var{class} is neither a class object nor a type object, a |
| 316 | \code{TypeError} exception is raised. |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 317 | \end{funcdesc} |
| 318 | |
| 319 | \begin{funcdesc}{issubclass}{class1, class2} |
| 320 | Return true if \var{class1} is a subclass (direct or indirect) of |
| 321 | \var{class2}. A class is considered a subclass of itself. If either |
| 322 | argument is not a class object, a \code{TypeError} exception is raised. |
| 323 | \end{funcdesc} |
| 324 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 325 | \begin{funcdesc}{len}{s} |
| 326 | Return the length (the number of items) of an object. The argument |
| 327 | may be a sequence (string, tuple or list) or a mapping (dictionary). |
| 328 | \end{funcdesc} |
| 329 | |
Guido van Rossum | 921f32c | 1997-06-02 17:21:20 +0000 | [diff] [blame] | 330 | \begin{funcdesc}{list}{sequence} |
| 331 | Return a list whose items are the same and in the same order as |
| 332 | \var{sequence}'s items. If \var{sequence} is already a list, |
| 333 | a copy is made and returned, similar to \code{\var{sequence}[:]}. |
| 334 | For instance, \code{list('abc')} returns |
| 335 | returns \code{['a', 'b', 'c']} and \code{list( (1, 2, 3) )} returns |
| 336 | \code{[1, 2, 3]}. |
| 337 | \end{funcdesc} |
| 338 | |
Guido van Rossum | fb502e9 | 1995-07-07 22:58:28 +0000 | [diff] [blame] | 339 | \begin{funcdesc}{locals}{} |
| 340 | Return a dictionary representing the current local symbol table. |
| 341 | Inside a function, modifying this dictionary does not always have the |
| 342 | desired effect. |
| 343 | \end{funcdesc} |
| 344 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 345 | \begin{funcdesc}{long}{x} |
Guido van Rossum | 1cd26f2 | 1997-04-02 06:04:02 +0000 | [diff] [blame] | 346 | Convert a string or number to a long integer. If the argument is a |
| 347 | string, it must contain a possibly singed decimal number of |
| 348 | arbitrary size, possibly embedded in whitespace; |
| 349 | this behaves identical to \code{string.atol(\var{x})}. |
| 350 | Otherwise, the argument may be a plain or |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 351 | 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] | 352 | the same value is returned. Conversion of floating |
| 353 | point numbers to integers is defined by the C semantics; |
| 354 | see the description of \code{int()}. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 355 | \end{funcdesc} |
| 356 | |
| 357 | \begin{funcdesc}{map}{function\, list\, ...} |
| 358 | Apply \var{function} to every item of \var{list} and return a list |
| 359 | of the results. If additional \var{list} arguments are passed, |
| 360 | \var{function} must take that many arguments and is applied to |
| 361 | the items of all lists in parallel; if a list is shorter than another |
| 362 | it is assumed to be extended with \code{None} items. If |
| 363 | \var{function} is \code{None}, the identity function is assumed; if |
| 364 | there are multiple list arguments, \code{map} returns a list |
| 365 | consisting of tuples containing the corresponding items from all lists |
| 366 | (i.e. a kind of transpose operation). The \var{list} arguments may be |
| 367 | any kind of sequence; the result is always a list. |
| 368 | \end{funcdesc} |
| 369 | |
| 370 | \begin{funcdesc}{max}{s} |
| 371 | Return the largest item of a non-empty sequence (string, tuple or |
| 372 | list). |
| 373 | \end{funcdesc} |
| 374 | |
| 375 | \begin{funcdesc}{min}{s} |
| 376 | Return the smallest item of a non-empty sequence (string, tuple or |
| 377 | list). |
| 378 | \end{funcdesc} |
| 379 | |
| 380 | \begin{funcdesc}{oct}{x} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 381 | Convert an integer number (of any size) to an octal string. The |
Guido van Rossum | 5cd7520 | 1997-01-14 18:44:23 +0000 | [diff] [blame] | 382 | result is a valid Python expression. Note: this always yields |
| 383 | an unsigned literal, e.g. on a 32-bit machine, \code{oct(-1)} yields |
| 384 | \code{'037777777777'}. When evaluated on a machine with the same |
| 385 | word size, this literal is evaluated as -1; at a different word |
| 386 | size, it may turn up as a large positive number or raise an |
| 387 | \code{OverflowError} exception. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 388 | \end{funcdesc} |
| 389 | |
Guido van Rossum | 7f49b7a | 1995-01-12 12:38:46 +0000 | [diff] [blame] | 390 | \begin{funcdesc}{open}{filename\optional{\, mode\optional{\, bufsize}}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 391 | Return a new file object (described earlier under Built-in Types). |
Guido van Rossum | 041be05 | 1994-05-03 14:46:50 +0000 | [diff] [blame] | 392 | The first two arguments are the same as for \code{stdio}'s |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 393 | \code{fopen()}: \var{filename} is the file name to be opened, |
| 394 | \var{mode} indicates how the file is to be opened: \code{'r'} for |
| 395 | reading, \code{'w'} for writing (truncating an existing file), and |
Guido van Rossum | 1dde7b7 | 1996-10-11 15:57:17 +0000 | [diff] [blame] | 396 | \code{'a'} opens it for appending (which on {\em some} \UNIX{} |
Guido van Rossum | 59b328e | 1996-05-02 15:16:59 +0000 | [diff] [blame] | 397 | systems means that {\em all} writes append to the end of the file, |
| 398 | regardless of the current seek position). |
| 399 | Modes \code{'r+'}, \code{'w+'} and |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 400 | \code{'a+'} open the file for updating, provided the underlying |
| 401 | \code{stdio} library understands this. On systems that differentiate |
| 402 | between binary and text files, \code{'b'} appended to the mode opens |
| 403 | the file in binary mode. If the file cannot be opened, \code{IOError} |
| 404 | is raised. |
Guido van Rossum | 041be05 | 1994-05-03 14:46:50 +0000 | [diff] [blame] | 405 | If \var{mode} is omitted, it defaults to \code{'r'}. |
| 406 | The optional \var{bufsize} argument specifies the file's desired |
| 407 | buffer size: 0 means unbuffered, 1 means line buffered, any other |
| 408 | positive value means use a buffer of (approximately) that size. A |
| 409 | negative \var{bufsize} means to use the system default, which is |
| 410 | usually line buffered for for tty devices and fully buffered for other |
| 411 | files.% |
| 412 | \footnote{Specifying a buffer size currently has no effect on systems |
| 413 | that don't have \code{setvbuf()}. The interface to specify the buffer |
| 414 | size is not done using a method that calls \code{setvbuf()}, because |
| 415 | that may dump core when called after any I/O has been performed, and |
| 416 | there's no reliable way to determine whether this is the case.} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 417 | \end{funcdesc} |
| 418 | |
| 419 | \begin{funcdesc}{ord}{c} |
| 420 | Return the \ASCII{} value of a string of one character. E.g., |
| 421 | \code{ord('a')} returns the integer \code{97}. This is the inverse of |
| 422 | \code{chr()}. |
| 423 | \end{funcdesc} |
| 424 | |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 425 | \begin{funcdesc}{pow}{x\, y\optional{\, z}} |
Guido van Rossum | b8b264b | 1994-08-12 13:13:50 +0000 | [diff] [blame] | 426 | Return \var{x} to the power \var{y}; if \var{z} is present, return |
| 427 | \var{x} to the power \var{y}, modulo \var{z} (computed more |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 428 | efficiently than \code{pow(\var{x}, \var{y}) \% \var{z}}). |
Guido van Rossum | b8b264b | 1994-08-12 13:13:50 +0000 | [diff] [blame] | 429 | The arguments must have |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 430 | numeric types. With mixed operand types, the rules for binary |
| 431 | arithmetic operators apply. The effective operand type is also the |
| 432 | type of the result; if the result is not expressible in this type, the |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 433 | function raises an exception; e.g., \code{pow(2, -1)} or \code{pow(2, |
| 434 | 35000)} is not allowed. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 435 | \end{funcdesc} |
| 436 | |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 437 | \begin{funcdesc}{range}{\optional{start\,} stop\optional{\, step}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 438 | This is a versatile function to create lists containing arithmetic |
| 439 | progressions. It is most often used in \code{for} loops. The |
| 440 | arguments must be plain integers. If the \var{step} argument is |
| 441 | omitted, it defaults to \code{1}. If the \var{start} argument is |
| 442 | omitted, it defaults to \code{0}. The full form returns a list of |
| 443 | plain integers \code{[\var{start}, \var{start} + \var{step}, |
| 444 | \var{start} + 2 * \var{step}, \ldots]}. If \var{step} is positive, |
| 445 | the last element is the largest \code{\var{start} + \var{i} * |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 446 | \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] | 447 | element is the largest \code{\var{start} + \var{i} * \var{step}} |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 448 | greater than \var{stop}. \var{step} must not be zero (or else an |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 449 | exception is raised). Example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 450 | |
| 451 | \bcode\begin{verbatim} |
| 452 | >>> range(10) |
| 453 | [0, 1, 2, 3, 4, 5, 6, 7, 8, 9] |
| 454 | >>> range(1, 11) |
| 455 | [1, 2, 3, 4, 5, 6, 7, 8, 9, 10] |
| 456 | >>> range(0, 30, 5) |
| 457 | [0, 5, 10, 15, 20, 25] |
| 458 | >>> range(0, 10, 3) |
| 459 | [0, 3, 6, 9] |
| 460 | >>> range(0, -10, -1) |
| 461 | [0, -1, -2, -3, -4, -5, -6, -7, -8, -9] |
| 462 | >>> range(0) |
| 463 | [] |
| 464 | >>> range(1, 0) |
| 465 | [] |
| 466 | >>> |
| 467 | \end{verbatim}\ecode |
| 468 | \end{funcdesc} |
| 469 | |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 470 | \begin{funcdesc}{raw_input}{\optional{prompt}} |
| 471 | If the \var{prompt} argument is present, it is written to standard output |
| 472 | without a trailing newline. The function then reads a line from input, |
| 473 | converts it to a string (stripping a trailing newline), and returns that. |
| 474 | When \EOF{} is read, \code{EOFError} is raised. Example: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 475 | |
| 476 | \bcode\begin{verbatim} |
| 477 | >>> s = raw_input('--> ') |
| 478 | --> Monty Python's Flying Circus |
| 479 | >>> s |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 480 | "Monty Python's Flying Circus" |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 481 | >>> |
| 482 | \end{verbatim}\ecode |
Guido van Rossum | 921f32c | 1997-06-02 17:21:20 +0000 | [diff] [blame] | 483 | |
Guido van Rossum | eb0f066 | 1997-12-30 20:38:16 +0000 | [diff] [blame] | 484 | If the \code{readline} module was loaded, then |
Guido van Rossum | 921f32c | 1997-06-02 17:21:20 +0000 | [diff] [blame] | 485 | \code{raw_input()} will use it to provide elaborate |
| 486 | line editing and history features. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 487 | \end{funcdesc} |
| 488 | |
Guido van Rossum | 16d6e71 | 1994-08-08 12:30:22 +0000 | [diff] [blame] | 489 | \begin{funcdesc}{reduce}{function\, list\optional{\, initializer}} |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 490 | Apply the binary \var{function} to the items of \var{list} so as to |
| 491 | reduce the list to a single value. E.g., |
| 492 | \code{reduce(lambda x, y: x*y, \var{list}, 1)} returns the product of |
| 493 | the elements of \var{list}. The optional \var{initializer} can be |
| 494 | thought of as being prepended to \var{list} so as to allow reduction |
| 495 | of an empty \var{list}. The \var{list} arguments may be any kind of |
| 496 | sequence. |
| 497 | \end{funcdesc} |
| 498 | |
| 499 | \begin{funcdesc}{reload}{module} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 500 | Re-parse and re-initialize an already imported \var{module}. The |
| 501 | argument must be a module object, so it must have been successfully |
| 502 | imported before. This is useful if you have edited the module source |
| 503 | file using an external editor and want to try out the new version |
| 504 | without leaving the Python interpreter. The return value is the |
| 505 | module object (i.e.\ the same as the \var{module} argument). |
| 506 | |
| 507 | There are a number of caveats: |
| 508 | |
| 509 | If a module is syntactically correct but its initialization fails, the |
| 510 | first \code{import} statement for it does not bind its name locally, |
| 511 | but does store a (partially initialized) module object in |
| 512 | \code{sys.modules}. To reload the module you must first |
| 513 | \code{import} it again (this will bind the name to the partially |
| 514 | initialized module object) before you can \code{reload()} it. |
| 515 | |
| 516 | When a module is reloaded, its dictionary (containing the module's |
| 517 | global variables) is retained. Redefinitions of names will override |
| 518 | the old definitions, so this is generally not a problem. If the new |
| 519 | version of a module does not define a name that was defined by the old |
| 520 | version, the old definition remains. This feature can be used to the |
| 521 | module's advantage if it maintains a global table or cache of objects |
| 522 | --- with a \code{try} statement it can test for the table's presence |
| 523 | and skip its initialization if desired. |
| 524 | |
| 525 | It is legal though generally not very useful to reload built-in or |
| 526 | dynamically loaded modules, except for \code{sys}, \code{__main__} and |
| 527 | \code{__builtin__}. In certain cases, however, extension modules are |
| 528 | not designed to be initialized more than once, and may fail in |
| 529 | arbitrary ways when reloaded. |
| 530 | |
| 531 | If a module imports objects from another module using \code{from} |
Fred Drake | 4b3f031 | 1996-12-13 22:04:31 +0000 | [diff] [blame] | 532 | \ldots{} \code{import} \ldots{}, calling \code{reload()} for the other |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 533 | module does not redefine the objects imported from it --- one way |
| 534 | around this is to re-execute the \code{from} statement, another is to |
| 535 | use \code{import} and qualified names (\var{module}.\var{name}) |
| 536 | instead. |
| 537 | |
| 538 | If a module instantiates instances of a class, reloading the module |
| 539 | that defines the class does not affect the method definitions of the |
| 540 | instances --- they continue to use the old class definition. The same |
| 541 | is true for derived classes. |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 542 | \end{funcdesc} |
| 543 | |
| 544 | \begin{funcdesc}{repr}{object} |
| 545 | Return a string containing a printable representation of an object. |
| 546 | This is the same value yielded by conversions (reverse quotes). |
| 547 | It is sometimes useful to be able to access this operation as an |
| 548 | ordinary function. For many types, this function makes an attempt |
| 549 | to return a string that would yield an object with the same value |
| 550 | when passed to \code{eval()}. |
| 551 | \end{funcdesc} |
| 552 | |
| 553 | \begin{funcdesc}{round}{x\, n} |
| 554 | Return the floating point value \var{x} rounded to \var{n} digits |
| 555 | after the decimal point. If \var{n} is omitted, it defaults to zero. |
| 556 | The result is a floating point number. Values are rounded to the |
| 557 | closest multiple of 10 to the power minus \var{n}; if two multiples |
| 558 | are equally close, rounding is done away from 0 (so e.g. |
| 559 | \code{round(0.5)} is \code{1.0} and \code{round(-0.5)} is \code{-1.0}). |
| 560 | \end{funcdesc} |
| 561 | |
| 562 | \begin{funcdesc}{setattr}{object\, name\, value} |
| 563 | This is the counterpart of \code{getattr}. The arguments are an |
| 564 | object, a string and an arbitrary value. The string must be the name |
| 565 | of one of the object's attributes. The function assigns the value to |
| 566 | the attribute, provided the object allows it. For example, |
| 567 | \code{setattr(\var{x}, '\var{foobar}', 123)} is equivalent to |
| 568 | \code{\var{x}.\var{foobar} = 123}. |
| 569 | \end{funcdesc} |
| 570 | |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 571 | \begin{funcdesc}{slice}{\optional{start\,} stop\optional{\, step}} |
| 572 | Return a slice object representing the set of indices specified by |
| 573 | \code{range(\var{start}, \var{stop}, \var{step})}. The \var{start} |
| 574 | and \var{step} arguments default to None. Slice objects have |
| 575 | read-only data attributes \code{start}, \code{stop} and \code{step} |
| 576 | which merely return the argument values (or their default). They have |
| 577 | no other explicit functionality; however they are used by Numerical |
| 578 | Python and other third party extensions. Slice objects are also |
| 579 | generated when extended indexing syntax is used, e.g. for |
| 580 | \code{a[start:stop:step]} or \code{a[start:stop, i]}. |
| 581 | \end{funcdesc} |
| 582 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 583 | \begin{funcdesc}{str}{object} |
| 584 | Return a string containing a nicely printable representation of an |
| 585 | object. For strings, this returns the string itself. The difference |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 586 | with \code{repr(\var{object})} is that \code{str(\var{object})} does not |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 587 | always attempt to return a string that is acceptable to \code{eval()}; |
| 588 | its goal is to return a printable string. |
| 589 | \end{funcdesc} |
| 590 | |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 591 | \begin{funcdesc}{tuple}{sequence} |
Guido van Rossum | b8b264b | 1994-08-12 13:13:50 +0000 | [diff] [blame] | 592 | Return a tuple whose items are the same and in the same order as |
Guido van Rossum | 921f32c | 1997-06-02 17:21:20 +0000 | [diff] [blame] | 593 | \var{sequence}'s items. If \var{sequence} is already a tuple, it |
Guido van Rossum | b8b264b | 1994-08-12 13:13:50 +0000 | [diff] [blame] | 594 | is returned unchanged. For instance, \code{tuple('abc')} returns |
| 595 | returns \code{('a', 'b', 'c')} and \code{tuple([1, 2, 3])} returns |
| 596 | \code{(1, 2, 3)}. |
| 597 | \end{funcdesc} |
| 598 | |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 599 | \begin{funcdesc}{type}{object} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 600 | Return the type of an \var{object}. The return value is a type |
| 601 | object. The standard module \code{types} defines names for all |
| 602 | built-in types. |
Fred Drake | e14388c | 1997-12-15 22:28:38 +0000 | [diff] [blame] | 603 | \refstmodindex{types} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 604 | \obindex{type} |
| 605 | For instance: |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 606 | |
| 607 | \bcode\begin{verbatim} |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 608 | >>> import types |
Fred Drake | fd49a96 | 1998-01-11 21:15:23 +0000 | [diff] [blame^] | 609 | >>> if isinstance(x, types.StringType): print "It's a string" |
Guido van Rossum | 5fdeeea | 1994-01-02 01:22:07 +0000 | [diff] [blame] | 610 | \end{verbatim}\ecode |
| 611 | \end{funcdesc} |
Guido van Rossum | 68cfbe7 | 1994-02-24 11:28:27 +0000 | [diff] [blame] | 612 | |
Guido van Rossum | 6bb1adc | 1995-03-13 10:03:32 +0000 | [diff] [blame] | 613 | \begin{funcdesc}{vars}{\optional{object}} |
Guido van Rossum | 1738311 | 1994-04-21 10:32:28 +0000 | [diff] [blame] | 614 | Without arguments, return a dictionary corresponding to the current |
| 615 | local symbol table. With a module, class or class instance object as |
| 616 | argument (or anything else that has a \code{__dict__} attribute), |
| 617 | returns a dictionary corresponding to the object's symbol table. |
| 618 | The returned dictionary should not be modified: the effects on the |
| 619 | corresponding symbol table are undefined.% |
| 620 | \footnote{In the current implementation, local variable bindings |
| 621 | cannot normally be affected this way, but variables retrieved from |
Guido van Rossum | 6c4f003 | 1995-03-07 10:14:09 +0000 | [diff] [blame] | 622 | other scopes (e.g. modules) can be. This may change.} |
Guido van Rossum | 1738311 | 1994-04-21 10:32:28 +0000 | [diff] [blame] | 623 | \end{funcdesc} |
| 624 | |
Guido van Rossum | 7974b0f | 1997-10-05 18:53:00 +0000 | [diff] [blame] | 625 | \begin{funcdesc}{xrange}{\optional{start\,} stop\optional{\, step}} |
Guido van Rossum | 68cfbe7 | 1994-02-24 11:28:27 +0000 | [diff] [blame] | 626 | This function is very similar to \code{range()}, but returns an |
| 627 | ``xrange object'' instead of a list. This is an opaque sequence type |
| 628 | which yields the same values as the corresponding list, without |
| 629 | actually storing them all simultaneously. The advantage of |
| 630 | \code{xrange()} over \code{range()} is minimal (since \code{xrange()} |
| 631 | still has to create the values when asked for them) except when a very |
Guido van Rossum | 470be14 | 1995-03-17 16:07:09 +0000 | [diff] [blame] | 632 | large range is used on a memory-starved machine (e.g. MS-DOS) or when all |
Guido van Rossum | 68cfbe7 | 1994-02-24 11:28:27 +0000 | [diff] [blame] | 633 | of the range's elements are never used (e.g. when the loop is usually |
| 634 | terminated with \code{break}). |
| 635 | \end{funcdesc} |