Python 3.2.1官方函数手册：全面指南

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本Python函数参考手册详细介绍了Python 3.2.1版本的内置功能、常量、类型以及相关服务模块。它由Guido van Rossum编写，Fred L. Drake Jr.担任编辑，发布日期为2011年7月19日，由Python Software Foundation提供。手册的主要内容包括： 1. **介绍**：这部分可能涵盖了Python语言的基本概念，函数的作用以及为何它们在编程中的重要性。 2. **内置函数**：这部分列举了Python语言中预定义的功能，如用于真理值测试（如`if`语句的基础），布尔运算符（`and`, `or`, `not`），比较操作，数值类型（整数、浮点数、复数）等。 3. **内置常量**：讲解了Python中的预设常量，如`True`和`False`，以及由site模块新增的其他常量。 4. **内置类型**：详细解释了不同类型的对象，如序列（字符串、字节、列表、元组、范围）、集合（set和frozenset）、映射（字典）和内存视图（memoryview）。此外，还涉及上下文管理器（ContextManager）和其他特殊类型的特性。 5. **内置异常**：这部分列出了Python的异常类别及其层次结构，帮助开发者理解和处理程序运行时可能出现的错误。 6. **字符串服务**：提供了字符串操作的工具，如标准库中的`string`模块（字符串操作），正则表达式操作（`re`模块），以及文本处理和填充功能（`textwrap`模块）。 7. **编码与解码**：通过`codecs`模块，手册介绍了编码注册表和基础类，以及与Unicode数据相关的`unicodedata`模块。这些内容覆盖了Python编程的核心要素，为学习者和开发者提供了全面的函数和工具参考，无论是初次接触Python还是深入探索其高级特性，都是不可或缺的参考资料。通过阅读和理解这些章节，用户可以提升对Python函数的熟练运用，以及在实际项目中高效利用标准库的能力。

The Python Library Reference, Release 3.2.1

ascii(object)

As repr(), return a string containing a printable representation of an object, but escape the non-ASCII char-

acters in the string returned by repr() using \x, \u or \U escapes. This generates a string similar to that

returned by repr() in Python 2.

bin(x)

Convert an integer number to a binary string. The result is a valid Python expression. If x is not a Python int

object, it has to deﬁne an __index__() method that returns an integer.

bool([x ])

Convert a value to a Boolean, using the standard truth testing procedure. If x is false or omitted, this returns

False; otherwise it returns True. bool is also a class, which is a subclass of int. Class bool cannot be

subclassed further. Its only instances are False and True.

bytearray([source[, encoding[, errors ]]])

Return a new array of bytes. The bytearray type is a mutable sequence of integers in the range 0 <= x < 256.

It has most of the usual methods of mutable sequences, described in Mutable Sequence Types, as well as most

methods that the bytes type has, see Bytes and Byte Array Methods.

The optional source parameter can be used to initialize the array in a few different ways:

•If it is a string, you must also give the encoding (and optionally, errors) parameters; bytearray() then

converts the string to bytes using str.encode().

•If it is an integer, the array will have that size and will be initialized with null bytes.

•If it is an object conforming to the buffer interface, a read-only buffer of the object will be used to initialize

the bytes array.

•If it is an iterable, it must be an iterable of integers in the range 0 <= x < 256, which are used as the

initial contents of the array.

Without an argument, an array of size 0 is created.

bytes([source[, encoding[, errors ]]])

Return a new “bytes” object, which is an immutable sequence of integers in the range 0 <= x < 256. bytes

is an immutable version of bytearray – it has the same non-mutating methods and the same indexing and

slicing behavior.

Accordingly, constructor arguments are interpreted as for bytearray().

Bytes objects can also be created with literals, see strings.

callable(object)

Return True if the object argument appears callable, False if not. If this returns true, it is still possible that

a call fails, but if it is false, calling object will never succeed. Note that classes are callable (calling a class

returns a new instance); instances are callable if their class has a __call__() method. New in version 3.2:

This function was ﬁrst removed in Python 3.0 and then brought back in Python 3.2.

chr(i)

Return the string representing a character whose Unicode codepoint is the integer i. For example, chr(97)

returns the string ’a’. This is the inverse of ord(). The valid range for the argument is from 0 through

1,114,111 (0x10FFFF in base 16). ValueError will be raised if i is outside that range.

Note that on narrow Unicode builds, the result is a string of length two for i greater than 65,535 (0xFFFF in

hexadecimal).

classmethod(function)

Return a class method for function.

A class method receives the class as implicit ﬁrst argument, just like an instance method receives the instance.

To declare a class method, use this idiom:

6 Chapter 2. Built-in Functions

The Python Library Reference, Release 3.2.1

class C:

@classmethod

def f(cls, arg1, arg2, ...): ...

The @classmethod form is a function decorator – see the description of function deﬁnitions in function for

details.

It can be called either on the class (such as C.f()) or on an instance (such as C().f()). The instance is

ignored except for its class. If a class method is called for a derived class, the derived class object is passed as

the implied ﬁrst argument.

Class methods are different than C++ or Java static methods. If you want those, see staticmethod() in this

section.

For more information on class methods, consult the documentation on the standard type hierarchy in types.

compile(source, ﬁlename, mode, ﬂags=0, dont_inherit=False, optimize=-1)

Compile the source into a code or AST object. Code objects can be executed by exec() or eval(). source

can either be a string or an AST object. Refer to the ast module documentation for information on how to

work with AST objects.

The ﬁlename argument should give the ﬁle from which the code was read; pass some recognizable value if it

wasn’t read from a ﬁle (’<string>’ is commonly used).

The mode argument speciﬁes what kind of code must be compiled; it can be ’exec’ if source consists of a

sequence of statements, ’eval’ if it consists of a single expression, or ’single’ if it consists of a single

interactive statement (in the latter case, expression statements that evaluate to something other than None will

be printed).

The optional arguments ﬂags and dont_inherit control which future statements (see PEP 236) affect the compi-

lation of source. If neither is present (or both are zero) the code is compiled with those future statements that are

in effect in the code that is calling compile. If the ﬂags argument is given and dont_inherit is not (or is zero) then

the future statements speciﬁed by the ﬂags argument are used in addition to those that would be used anyway.

If dont_inherit is a non-zero integer then the ﬂags argument is it – the future statements in effect around the call

to compile are ignored.

Future statements are speciﬁed by bits which can be bitwise ORed together to specify multiple statements. The

bitﬁeld required to specify a given feature can be found as the compiler_flag attribute on the _Feature

instance in the __future__ module.

The argument optimize speciﬁes the optimization level of the compiler; the default value of -1 selects the

optimization level of the interpreter as given by -O options. Explicit levels are 0 (no optimization; __debug__

is true), 1 (asserts are removed, __debug__ is false) or 2 (docstrings are removed too).

This function raises SyntaxError if the compiled source is invalid, and TypeError if the source contains

null bytes.

Note: When compiling a string with multi-line code in ’single’ or ’eval’ mode, input must be terminated

by at least one newline character. This is to facilitate detection of incomplete and complete statements in the

code module.

Changed in version 3.2: Allowed use of Windows and Mac newlines. Also input in ’exec’ mode does not

have to end in a newline anymore. Added the optimize parameter.

complex([real[, imag ]])

Create a complex number with the value real + imag*j or convert a string or number to a complex number. If

the ﬁrst parameter is a string, it will be interpreted as a complex number and the function must be called without

a second parameter. The second parameter can never be a string. Each argument may be any numeric type

The Python Library Reference, Release 3.2.1

(including complex). If imag is omitted, it defaults to zero and the function serves as a numeric conversion

function like int() and float(). If both arguments are omitted, returns 0j.

The complex type is described in Numeric Types — int, ﬂoat, complex.

delattr(object, name)

This is a relative of setattr(). The arguments are an object and a string. The string must be the name of one

of the object’s attributes. The function deletes the named attribute, provided the object allows it. For example,

delattr(x, ’foobar’) is equivalent to del x.foobar.

dict([arg ])

Create a new data dictionary, optionally with items taken from arg. The dictionary type is described in Mapping

Types — dict.

For other containers see the built in list, set, and tuple classes, and the collections module.

dir([object ])

Without arguments, return the list of names in the current local scope. With an argument, attempt to return a list

of valid attributes for that object.

If the object has a method named __dir__(), this method will be called and must return the list of attributes.

This allows objects that implement a custom __getattr__() or __getattribute__() function to cus-

tomize the way dir() reports their attributes.

If the object does not provide __dir__(), the function tries its best to gather information from the object’s

__dict__ attribute, if deﬁned, and from its type object. The resulting list is not necessarily complete, and

may be inaccurate when the object has a custom __getattr__().

The default dir() mechanism behaves differently with different types of objects, as it attempts to produce the

most relevant, rather than complete, information:

•If the object is a module object, the list contains the names of the module’s attributes.

•If the object is a type or class object, the list contains the names of its attributes, and recursively of the

attributes of its bases.

•Otherwise, the list contains the object’s attributes’ names, the names of its class’s attributes, and recursively

of the attributes of its class’s base classes.

The resulting list is sorted alphabetically. For example:

>>> import struct

>>> dir() # show the names in the module namespace

[’__builtins__’, ’__doc__’, ’__name__’, ’struct’]

>>> dir(struct) # show the names in the struct module

[’Struct’, ’__builtins__’, ’__doc__’, ’__file__’, ’__name__’,

’__package__’, ’_clearcache’, ’calcsize’, ’error’, ’pack’, ’pack_into’,

’unpack’, ’unpack_from’]

>>> class Shape(object):

def __dir__(self):

return [’area’, ’perimeter’, ’location’]

>>> s = Shape()

>>> dir(s)

[’area’, ’perimeter’, ’location’]

Note: Because dir() is supplied primarily as a convenience for use at an interactive prompt, it tries to supply

an interesting set of names more than it tries to supply a rigorously or consistently deﬁned set of names, and its

detailed behavior may change across releases. For example, metaclass attributes are not in the result list when

the argument is a class.

8 Chapter 2. Built-in Functions

The Python Library Reference, Release 3.2.1

divmod(a, b)

Take two (non complex) numbers as arguments and return a pair of numbers consisting of their quotient and

remainder when using integer division. With mixed operand types, the rules for binary arithmetic operators

apply. For integers, the result is the same as (a // b, a % b). For ﬂoating point numbers the result is (q,

a % b), where q is usually math.floor(a / b) but may be 1 less than that. In any case q

b + a %

b is very close to a, if a % b is non-zero it has the same sign as b, and 0 <= abs(a % b) < abs(b).

enumerate(iterable, start=0)

Return an enumerate object. iterable must be a sequence, an iterator, or some other object which supports

iteration. The __next__() method of the iterator returned by enumerate() returns a tuple containing a

count (from start which defaults to 0) and the values obtained from iterating over iterable.

>>> seasons = [’Spring’, ’Summer’, ’Fall’, ’Winter’]

>>> list(enumerate(seasons))

[(0, ’Spring’), (1, ’Summer’), (2, ’Fall’), (3, ’Winter’)]

>>> list(enumerate(seasons, start=1))

[(1, ’Spring’), (2, ’Summer’), (3, ’Fall’), (4, ’Winter’)]

Equivalent to:

def enumerate(sequence, start=0):

n = start

for elem in sequence:

yield n, elem

n += 1

eval(expression, globals=None, locals=None)

The arguments are a string and optional globals and locals. If provided, globals must be a dictionary. If provided,

locals can be any mapping object.

The expression argument is parsed and evaluated as a Python expression (technically speaking, a condition list)

using the globals and locals dictionaries as global and local namespace. If the globals dictionary is present

and lacks ‘__builtins__’, the current globals are copied into globals before expression is parsed. This means

that expression normally has full access to the standard builtins module and restricted environments are

propagated. If the locals dictionary is omitted it defaults to the globals dictionary. If both dictionaries are

omitted, the expression is executed in the environment where eval() is called. The return value is the result

of the evaluated expression. Syntax errors are reported as exceptions. Example:

>>> x = 1

>>> eval(’x+1’)

This function can also be used to execute arbitrary code objects (such as those created by compile()). In

this case pass a code object instead of a string. If the code object has been compiled with ’exec’ as the mode

argument, eval()‘s return value will be None.

Hints: dynamic execution of statements is supported by the exec() function. The globals() and

locals() functions returns the current global and local dictionary, respectively, which may be useful to pass

around for use by eval() or exec().

See ast.literal_eval() for a function that can safely evaluate strings with expressions containing only

literals.

exec(object[, globals[, locals ]])

This function supports dynamic execution of Python code. object must be either a string or a code object. If it is

The Python Library Reference, Release 3.2.1

a string, the string is parsed as a suite of Python statements which is then executed (unless a syntax error occurs).

If it is a code object, it is simply executed. In all cases, the code that’s executed is expected to be valid as ﬁle

input (see the section “File input” in the Reference Manual). Be aware that the return and yield statements

may not be used outside of function deﬁnitions even within the context of code passed to the exec() function.

The return value is None.

In all cases, if the optional parts are omitted, the code is executed in the current scope. If only globals is

provided, it must be a dictionary, which will be used for both the global and the local variables. If globals and

locals are given, they are used for the global and local variables, respectively. If provided, locals can be any

mapping object.

If the globals dictionary does not contain a value for the key __builtins__, a reference to the dictionary of

the built-in module builtins is inserted under that key. That way you can control what builtins are available to

the executed code by inserting your own __builtins__ dictionary into globals before passing it to exec().

Note: The built-in functions globals() and locals() return the current global and local dictionary,

respectively, which may be useful to pass around for use as the second and third argument to exec().

Note: The default locals act as described for function locals() below: modiﬁcations to the default locals

dictionary should not be attempted. Pass an explicit locals dictionary if you need to see effects of the code on

locals after function exec() returns.

filter(function, iterable)

Construct an iterator from those elements of iterable for which function returns true. iterable may be either

a sequence, a container which supports iteration, or an iterator. If function is None, the identity function is

assumed, that is, all elements of iterable that are false are removed.

Note that filter(function, iterable) is equivalent to the generator expression (item for

item in iterable if function(item)) if function is not None and (item for item in

iterable if item) if function is None.

See itertools.filterfalse() for the complementary function that returns elements of iterable for

which function returns false.

float([x ])

Convert a string or a number to ﬂoating point.

If the argument is a string, it should contain a decimal number, optionally preceded by a sign, and optionally

embedded in whitespace. The optional sign may be ’+’ or ’-’; a ’+’ sign has no effect on the value produced.

The argument may also be a string representing a NaN (not-a-number), or a positive or negative inﬁnity. More

precisely, the input must conform to the following grammar after leading and trailing whitespace characters are

removed:

sign ::= “+” | “-“

infinity ::= “Infinity” | “inf”

nan ::= “nan”

numeric_value ::= floatnumber | infinity | nan

numeric_string ::= [sign] numeric_value

Here floatnumber is the form of a Python ﬂoating-point literal, described in ﬂoating. Case is not signiﬁcant,

so, for example, “inf”, “Inf”, “INFINITY” and “iNfINity” are all acceptable spellings for positive inﬁnity.

Otherwise, if the argument is an integer or a ﬂoating point number, a ﬂoating point number with the same value

(within Python’s ﬂoating point precision) is returned. If the argument is outside the range of a Python ﬂoat, an

Note that the parser only accepts the Unix-style end of line convention. If you are reading the code from a ﬁle, make sure to use newline

conversion mode to convert Windows or Mac-style newlines.

10 Chapter 2. Built-in Functions

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