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| 55 | <H1><A NAME="SECTION004200000000000000000"></A><A NAME="non-essential-built-in-funcs"></A> |
| 56 | <BR> |
| 57 | 2.2 Non-essential Built-in Functions |
| 58 | </H1> |
| 59 | |
| 60 | <P> |
| 61 | There are several built-in functions that are no longer essential to learn, |
| 62 | know or use in modern Python programming. They have been kept here to |
| 63 | maintain backwards compatibility with programs written for older versions |
| 64 | of Python. |
| 65 | |
| 66 | <P> |
| 67 | Python programmers, trainers, students and bookwriters should feel free to |
| 68 | bypass these functions without concerns about missing something important. |
| 69 | |
| 70 | <P> |
| 71 | |
| 72 | <P> |
| 73 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 74 | <td><nobr><b><tt id='l2h-85' xml:id='l2h-85' class="function">apply</tt></b>(</nobr></td> |
| 75 | <td><var>function, args</var><big>[</big><var>, keywords</var><big>]</big><var></var>)</td></tr></table></dt> |
| 76 | <dd> |
| 77 | The <var>function</var> argument must be a callable object (a |
| 78 | user-defined or built-in function or method, or a class object) and |
| 79 | the <var>args</var> argument must be a sequence. The <var>function</var> is |
| 80 | called with <var>args</var> as the argument list; the number of arguments |
| 81 | is the length of the tuple. |
| 82 | If the optional <var>keywords</var> argument is present, it must be a |
| 83 | dictionary whose keys are strings. It specifies keyword arguments |
| 84 | to be added to the end of the argument list. |
| 85 | Calling <tt class="function">apply()</tt> is different from just calling |
| 86 | <code><var>function</var>(<var>args</var>)</code>, since in that case there is always |
| 87 | exactly one argument. The use of <tt class="function">apply()</tt> is equivalent |
| 88 | to <code><var>function</var>(*<var>args</var>, **<var>keywords</var>)</code>. |
| 89 | Use of <tt class="function">apply()</tt> is not necessary since the ``extended call |
| 90 | syntax,'' as used in the last example, is completely equivalent. |
| 91 | |
| 92 | <P> |
| 93 | <div class="versionnote"><b>Deprecated since release 2.3.</b> |
| 94 | Use the extended call syntax instead, as described |
| 95 | above.</div><p></p> |
| 96 | </dl> |
| 97 | |
| 98 | <P> |
| 99 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 100 | <td><nobr><b><tt id='l2h-86' xml:id='l2h-86' class="function">buffer</tt></b>(</nobr></td> |
| 101 | <td><var>object</var><big>[</big><var>, offset</var><big>[</big><var>, size</var><big>]</big><var></var><big>]</big><var></var>)</td></tr></table></dt> |
| 102 | <dd> |
| 103 | The <var>object</var> argument must be an object that supports the buffer |
| 104 | call interface (such as strings, arrays, and buffers). A new buffer |
| 105 | object will be created which references the <var>object</var> argument. |
| 106 | The buffer object will be a slice from the beginning of <var>object</var> |
| 107 | (or from the specified <var>offset</var>). The slice will extend to the |
| 108 | end of <var>object</var> (or will have a length given by the <var>size</var> |
| 109 | argument). |
| 110 | </dl> |
| 111 | |
| 112 | <P> |
| 113 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 114 | <td><nobr><b><tt id='l2h-87' xml:id='l2h-87' class="function">coerce</tt></b>(</nobr></td> |
| 115 | <td><var>x, y</var>)</td></tr></table></dt> |
| 116 | <dd> |
| 117 | Return a tuple consisting of the two numeric arguments converted to |
| 118 | a common type, using the same rules as used by arithmetic |
| 119 | operations. If coercion is not possible, raise <tt class="exception">TypeError</tt>. |
| 120 | </dl> |
| 121 | |
| 122 | <P> |
| 123 | <dl><dt><table cellpadding="0" cellspacing="0"><tr valign="baseline"> |
| 124 | <td><nobr><b><tt id='l2h-88' xml:id='l2h-88' class="function">intern</tt></b>(</nobr></td> |
| 125 | <td><var>string</var>)</td></tr></table></dt> |
| 126 | <dd> |
| 127 | Enter <var>string</var> in the table of ``interned'' strings and return |
| 128 | the interned string - which is <var>string</var> itself or a copy. |
| 129 | Interning strings is useful to gain a little performance on |
| 130 | dictionary lookup - if the keys in a dictionary are interned, and |
| 131 | the lookup key is interned, the key comparisons (after hashing) can |
| 132 | be done by a pointer compare instead of a string compare. Normally, |
| 133 | the names used in Python programs are automatically interned, and |
| 134 | the dictionaries used to hold module, class or instance attributes |
| 135 | have interned keys. |
| 136 | <span class="versionnote">Changed in version 2.3: |
| 137 | Interned strings are not |
| 138 | immortal (like they used to be in Python 2.2 and before); |
| 139 | you must keep a reference to the return value of <tt class="function">intern()</tt> |
| 140 | around to benefit from it.</span> |
| 141 | |
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