2. 内置函数
***********

The Python interpreter has a number of functions built into it that
are always available.  They are listed here in alphabetical order.

+---------------------+-------------------+--------------------+-------------------+----------------------+
|                     |                   | 内置函数           |                   |                      |
|=====================|===================|====================|===================|======================|
| "abs()"             | "divmod()"        | "input()"          | "open()"          | "staticmethod()"     |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "all()"             | "enumerate()"     | "int()"            | "ord()"           | "str()"              |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "any()"             | "eval()"          | "isinstance()"     | "pow()"           | "sum()"              |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "basestring()"      | "execfile()"      | "issubclass()"     | "print()"         | "super()"            |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "bin()"             | "file()"          | "iter()"           | "property()"      | "tuple()"            |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "bool()"            | "filter()"        | "len()"            | "range()"         | "type()"             |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "bytearray()"       | "float()"         | "list()"           | "raw_input()"     | "unichr()"           |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "callable()"        | "format()"        | "locals()"         | "reduce()"        | "unicode()"          |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "chr()"             | "frozenset()"     | "long()"           | "reload()"        | "vars()"             |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "classmethod()"     | "getattr()"       | "map()"            | "repr()"          | "xrange()"           |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "cmp()"             | "globals()"       | "max()"            | "reversed()"      | "zip()"              |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "compile()"         | "hasattr()"       | "memoryview()"     | "round()"         | "__import__()"       |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "complex()"         | "hash()"          | "min()"            | "set()"           |                      |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "delattr()"         | "help()"          | "next()"           | "setattr()"       |                      |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "dict()"            | "hex()"           | "object()"         | "slice()"         |                      |
+---------------------+-------------------+--------------------+-------------------+----------------------+
| "dir()"             | "id()"            | "oct()"            | "sorted()"        |                      |
+---------------------+-------------------+--------------------+-------------------+----------------------+

In addition, there are other four built-in functions that are no
longer considered essential: "apply()", "buffer()", "coerce()", and
"intern()".  They are documented in the Non-essential Built-in
Functions section.

abs(x)

   Return the absolute value of a number.  The argument may be a plain
   or long integer or a floating point number.  If the argument is a
   complex number, its magnitude is returned.

all(iterable)

   如果 *iterable* 的所有元素为真（或迭代器为空），返回 "True" 。等价
   于:

      def all(iterable):
          for element in iterable:
              if not element:
                  return False
          return True

   2.5 新版功能.

any(iterable)

   如果 *iterable* 的任一元素为真则返回 "True"。 如果迭代器为空，返回
   "False"。 等价于:

      def any(iterable):
          for element in iterable:
              if element:
                  return True
          return False

   2.5 新版功能.

basestring()

   This abstract type is the superclass for "str" and "unicode". It
   cannot be called or instantiated, but it can be used to test
   whether an object is an instance of "str" or "unicode".
   "isinstance(obj, basestring)" is equivalent to "isinstance(obj,
   (str, unicode))".

   2.3 新版功能.

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.

   2.6 新版功能.

class bool([x])

   Return a Boolean value, i.e. one of "True" or "False".  *x* is
   converted 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".

   2.2.1 新版功能.

   在 2.3 版更改: If no argument is given, this function returns
   "False".

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

   Return a new array of bytes.  The "bytearray" class is a mutable
   sequence of integers in the range 0 <= x < 256.  It has most of the
   usual methods of mutable sequences, described in 可变序列类型, as
   well as most methods that the "str" type has, see 字符串的方法.

   可选形参 *source* 可以用不同的方式来初始化数组：

   * If it is *unicode*, you must also give the *encoding* (and
     optionally, *errors*) parameters; "bytearray()" then converts the
     unicode to bytes using "unicode.encode()".

   * 如果是一个 *integer*，会初始化大小为该数字的数组，并使用 null
     字 节填充。

   * 如果是一个符合 *buffer* 接口的对象，该对象的只读 buffer 会用来
     初 始化字节数组。

   * 如果是一个 *iterable* 可迭代对象，它的元素的范围必须是 "0 <= x
     < 256" 的整数，它会被用作数组的初始内容。

   如果没有实参，则创建大小为 0 的数组。

   2.6 新版功能.

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);
   class instances are callable if they have a "__call__()" method.

chr(i)

   Return a string of one character whose ASCII code is the integer
   *i*.  For example, "chr(97)" returns the string "'a'". This is the
   inverse of "ord()".  The argument must be in the range [0..255],
   inclusive; "ValueError" will be raised if *i* is outside that
   range. See also "unichr()".

classmethod(function)

   Return a class method for *function*.

   一个类方法把类自己作为第一个实参，就像一个实例方法把实例自己作为第
   一个实参。请用以下习惯来声明类方法:

      class C(object):
          @classmethod
          def f(cls, arg1, arg2, ...):
              ...

   "@classmethod" 这样的形式称为函数的 *decorator* – 详情参阅 函数定义
   。

   类方法的调用可以在类上进行 (例如 "C.f()") 也可以在实例上进行 (例如
   "C().f()")。 其所属类以外的类实例会被忽略。 如果类方法在其所属类的
   派生类上调用，则该派生类对象会被作为隐含的第一个参数被传入。

   类方法与 C++ 或 Java 中的静态方法不同。 如果你需要后者，请参阅
   "staticmethod()"。

   想了解更多有关类方法的信息，请参阅 标准类型层级结构 。

   2.2 新版功能.

   在 2.4 版更改: Function decorator syntax added.

cmp(x, y)

   Compare the two objects *x* and *y* and return an integer according
   to the outcome.  The return value is negative if "x < y", zero if
   "x == y" and strictly positive if "x > y".

compile(source, filename, mode[, flags[, dont_inherit]])

   Compile the *source* into a code or AST object.  Code objects can
   be executed by an "exec" statement or evaluated by a call to
   "eval()". *source* can either be a Unicode string, a *Latin-1*
   encoded string or an AST object. Refer to the "ast" module
   documentation for information on how to work with AST objects.

   *filename* 实参需要是代码读取的文件名；如果代码不需要从文件中读取，
   可以传入一些可辨识的值（经常会使用 "'<string>'"）。

   *mode* 实参指定了编译代码必须用的模式。如果 *source* 是语句序列，可
   以是 "'exec'"；如果是单一表达式，可以是 "'eval'"；如果是单个交互式
   语句，可以是 "'single'"。（在最后一种情况下，如果表达式执行结果不是
   "None" 将会被打印出来。）

   The optional arguments *flags* and *dont_inherit* control which
   future statements (see **PEP 236**) affect the compilation 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 语句使用比特位来指定，多个语句可以通过按位或来指定。具体特性
   的比特位可以通过 "__future__"  模块中的 "_Feature" 类的实例的
   "compiler_flag" 属性来获得。

   This function raises "SyntaxError" if the compiled source is
   invalid, and "TypeError" if the source contains null bytes.

   如果您想分析 Python 代码的 AST 表示，请参阅 "ast.parse()"。

   注解: 在 "'single'"  或 "'eval'" 模式编译多行代码字符串时，输入必
     须以至 少一个换行符结尾。 这使 "code" 模块更容易检测语句的完整性
     。

   警告: 在将足够大或者足够复杂的字符串编译成 AST 对象时，Python 解
     释器有 可以因为 Python AST 编译器的栈深度限制而崩溃。

   在 2.3 版更改: The *flags* and *dont_inherit* arguments were added.

   在 2.6 版更改: Support for compiling AST objects.

   在 2.7 版更改: Allowed use of Windows and Mac newlines.  Also input
   in "'exec'" mode does not have to end in a newline anymore.

class complex([real[, imag]])

   Return a complex number with the value *real* + *imag**1j 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 (including complex). If *imag* is omitted, it defaults
   to zero and the function serves as a numeric conversion function
   like "int()", "long()" and "float()".  If both arguments are
   omitted, returns "0j".

   注解: 当从字符串转换时，字符串在 "+" 或 "-" 的周围必须不能有空格
     。例如 "complex('1+2j')" 是合法的，但 "complex('1 + 2j')" 会触发
     "ValueError" 异常。

   Numeric Types — int, float, long, complex 描述了复数类型。

delattr(object, name)

   "setattr()" 相关的函数。实参是一个对象和一个字符串。该字符串必须是
   对象的某个属性。如果对象允许，该函数将删除指定的属性。例如
   "delattr(x, 'foobar')"  等价于 "del x.foobar" 。

class dict(**kwarg)
class dict(mapping, **kwarg)
class dict(iterable, **kwarg)

   创建一个新的字典。"dict" 对象是一个字典类。参见 "dict" 和 映射类型
   — dict 了解这个类。

   其他容器类型，请参见内置的 "list"、"set" 和 "tuple" 类，以及
   "collections" 模块。

dir([object])

   如果没有实参，则返回当前本地作用域中的名称列表。如果有实参，它会尝
   试返回该对象的有效属性列表。

   如果对象有一个名为 "__dir__()" 的方法，那么该方法将被调用，并且必须
   返回一个属性列表。这允许实现自定义 "__getattr__()" 或
   "__getattribute__()" 函数的对象能够自定义 "dir()" 来报告它们的属性
   。

   如果对象不提供 "__dir__()"，这个函数会尝试从对象已定义的 "__dict__"
   属性和类型对象收集信息。结果列表并不总是完整的，如果对象有自定义
   "__getattr__()"，那结果可能不准确。

   默认的 "dir()" 机制对不同类型的对象行为不同，它会试图返回最相关而不
   是最全的信息：

   * 如果对象是模块对象，则列表包含模块的属性名称。

   * 如果对象是类型或类对象，则列表包含它们的属性名称，并且递归查找
     所 有基类的属性。

   * 否则，列表包含对象的属性名称，它的类属性名称，并且递归查找它的
     类 的所有基类的属性。

   返回的列表按字母表排序。例如：

   >>> 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']

   注解: 因为 "dir()" 主要是为了便于在交互式时使用，所以它会试图返回
     人们感 兴趣的名字集合，而不是试图保证结果的严格性或一致性，它具体
     的行为 也可能在不同版本之间改变。例如，当实参是一个类时，
     metaclass 的属 性不包含在结果列表中。

divmod(a, b)

   Take two (non complex) numbers as arguments and return a pair of
   numbers consisting of their quotient and remainder when using long
   division.  With mixed operand types, the rules for binary
   arithmetic operators apply.  For plain and long 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)".

   在 2.3 版更改: Using "divmod()" with complex numbers is deprecated.

enumerate(sequence, start=0)

   Return an enumerate object. *sequence* 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 *sequence*:

      >>> 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')]

   等价于:

      def enumerate(sequence, start=0):
          n = start
          for elem in sequence:
              yield n, elem
              n += 1

   2.3 新版功能.

   在 2.6 版更改: The *start* parameter was added.

eval(expression[, globals[, locals]])

   The arguments are a Unicode or *Latin-1* encoded string and
   optional globals and locals.  If provided, *globals* must be a
   dictionary. If provided, *locals* can be any mapping object.

   在 2.4 版更改: formerly *locals* was required to be a dictionary.

   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 "__builtin__" 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
   >>> print eval('x+1')
   2

   这个函数也可以用来执行任何代码对象（如 "compile()"  创建的）。这种
   情况下，参数是代码对象，而不是字符串。如果编译该对象时的 *mode* 实
   参是 "'exec'" 那么 "eval()" 返回值为 "None" 。

   Hints: dynamic execution of statements is supported by the "exec"
   statement.  Execution of statements from a file is supported by the
   "execfile()" 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
   "execfile()".

   另外可以参阅 "ast.literal_eval()"，该函数可以安全执行仅包含文字的表
   达式字符串。

execfile(filename[, globals[, locals]])

   This function is similar to the "exec" statement, but parses a file
   instead of a string.  It is different from the "import" statement
   in that it does not use the module administration — it reads the
   file unconditionally and does not create a new module. [1]

   The arguments are a file name and two optional dictionaries.  The
   file is parsed and evaluated as a sequence of Python statements
   (similarly to a module) using the *globals* and *locals*
   dictionaries as global and local namespace. If provided, *locals*
   can be any mapping object.  Remember that at module level, globals
   and locals are the same dictionary. If two separate objects are
   passed as *globals* and *locals*, the code will be executed as if
   it were embedded in a class definition.

   在 2.4 版更改: formerly *locals* was required to be a dictionary.

   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 "execfile()" is called.  The
   return value is "None".

   注解: 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 "execfile()" returns.  "execfile()" cannot be used
     reliably to modify a function’s locals.

file(name[, mode[, buffering]])

   Constructor function for the "file" type, described further in
   section File Objects.  The constructor’s arguments are the same as
   those of the "open()" built-in function described below.

   When opening a file, it’s preferable to use "open()" instead of
   invoking this constructor directly.  "file" is more suited to type
   testing (for example, writing "isinstance(f, file)").

   2.2 新版功能.

filter(function, iterable)

   Construct a list 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 *iterable*
   is a string or a tuple, the result also has that type; otherwise it
   is always a list.  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 "[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.ifilter()" and "itertools.ifilterfalse()" for
   iterator versions of this function, including a variation that
   filters for elements where the *function* returns false.

class float([x])

   返回从数字或字符串 *x* 生成的浮点数。

   If the argument is a string, it must contain a possibly signed
   decimal or floating point number, possibly embedded in whitespace.
   The argument may also be [+|-]nan or [+|-]inf. Otherwise, the
   argument may be a plain or long integer or a floating point number,
   and a floating point number with the same value (within Python’s
   floating point precision) is returned.  If no argument is given,
   returns "0.0".

   注解: When passing in a string, values for NaN and Infinity may
     be returned, depending on the underlying C library.  Float
     accepts the strings nan, inf and -inf for NaN and positive or
     negative infinity. The case and a leading + are ignored as well
     as a leading - is ignored for NaN. Float always represents NaN
     and infinity as nan, inf or -inf.

   Numeric Types — int, float, long, complex 描述了浮点类型。

format(value[, format_spec])

   将 *value* 转换为 *format_spec* 控制的“格式化”表示。*format_spec*
   的解释取决于 *value* 实参的类型，但是大多数内置类型使用标准格式化语
   法：格式规格迷你语言。

   注解: "format(value, format_spec)" merely calls
     "value.__format__(format_spec)".

   2.6 新版功能.

class frozenset([iterable])

   返回一个新的 "frozenset" 对象，它包含可选参数 *iterable* 中的元素。
   "frozenset" 是一个内置的类。有关此类的文档，请参阅 "frozenset" 和
   集合类型 — set, frozenset。

   请参阅内建的 "set"、"list"、"tuple" 和 "dict" 类，以及
   "collections" 模块来了解其它的容器。

   2.4 新版功能.

getattr(object, name[, default])

   返回对象命名属性的值。*name* 必须是字符串。如果该字符串是对象的属性
   之一，则返回该属性的值。例如， "getattr(x, 'foobar')" 等同于
   "x.foobar"。如果指定的属性不存在，且提供了 *default* 值，则返回它，
   否则触发 "AttributeError"。

globals()

   返回表示当前全局符号表的字典。这总是当前模块的字典（在函数或方法中
   ，不是调用它的模块，而是定义它的模块）。

hasattr(object, name)

   The arguments are an object and a string.  The result is "True" if
   the string is the name of one of the object’s attributes, "False"
   if not. (This is implemented by calling "getattr(object, name)" and
   seeing whether it raises an exception or not.)

hash(object)

   Return the hash value of the object (if it has one).  Hash values
   are integers. They are used to quickly compare dictionary keys
   during a dictionary lookup. Numeric values that compare equal have
   the same hash value (even if they are of different types, as is the
   case for 1 and 1.0).

help([object])

   启动内置的帮助系统（此函数主要在交互式中使用）。如果没有实参，解释
   器控制台里会启动交互式帮助系统。如果实参是一个字符串，则在模块、函
   数、类、方法、关键字或文档主题中搜索该字符串，并在控制台上打印帮助
   信息。如果实参是其他任意对象，则会生成该对象的帮助页。

   该函数通过 "site" 模块加入到内置命名空间。

   2.2 新版功能.

hex(x)

   Convert an integer number (of any size) to a lowercase hexadecimal
   string prefixed with “0x”, for example:

   >>> hex(255)
   '0xff'
   >>> hex(-42)
   '-0x2a'
   >>> hex(1L)
   '0x1L'

   If x is not a Python "int" or "long" object, it has to define a
   __hex__() method that returns a string.

   另请参阅 "int()" 将十六进制字符串转换为以 16 为基数的整数。

   注解: 如果要获取浮点数的十六进制字符串形式，请使用 "float.hex()"
     方法。

   在 2.4 版更改: Formerly only returned an unsigned literal.

id(object)

   Return the “identity” of an object.  This is an integer (or long
   integer) which is guaranteed to be unique and constant for this
   object during its lifetime. Two objects with non-overlapping
   lifetimes may have the same "id()" value.

   **CPython implementation detail:** This is the address of the
   object in memory.

input([prompt])

   Equivalent to "eval(raw_input(prompt))".

   This function does not catch user errors. If the input is not
   syntactically valid, a "SyntaxError" will be raised. Other
   exceptions may be raised if there is an error during evaluation.

   如果加载了 "readline" 模块，"input()" 将使用它来提供复杂的行编辑和
   历史记录功能。

   Consider using the "raw_input()" function for general input from
   users.

class int(x=0)
class int(x, base=10)

   Return an integer object constructed from a number or string *x*,
   or return "0" if no arguments are given.  If *x* is a number, it
   can be a plain integer, a long integer, or a floating point number.
   If *x* is floating point, the conversion truncates towards zero.
   If the argument is outside the integer range, the function returns
   a long object instead.

   If *x* is not a number or if *base* is given, then *x* must be a
   string or Unicode object representing an integer literal in radix
   *base*.  Optionally, the literal can be preceded by "+" or "-"
   (with no space in between) and surrounded by whitespace.  A base-n
   literal consists of the digits 0 to n-1, with "a" to "z" (or "A" to
   "Z") having values 10 to 35.  The default *base* is 10. The allowed
   values are 0 and 2–36. Base-2, -8, and -16 literals can be
   optionally prefixed with "0b"/"0B", "0o"/"0O"/"0", or "0x"/"0X", as
   with integer literals in code. Base 0 means to interpret the string
   exactly as an integer literal, so that the actual base is 2, 8, 10,
   or 16.

   整数类型定义请参阅 Numeric Types — int, float, long, complex 。

isinstance(object, classinfo)

   Return true if the *object* argument is an instance of the
   *classinfo* argument, or of a (direct, indirect or *virtual*)
   subclass thereof.  Also return true if *classinfo* is a type object
   (new-style class) and *object* is an object of that type or of a
   (direct, indirect or *virtual*) subclass thereof.  If *object* is
   not a class instance or an object of the given type, the function
   always returns false. If *classinfo* is a tuple of class or type
   objects (or recursively, other such tuples), return true if
   *object* is an instance of any of the classes or types.  If
   *classinfo* is not a class, type, or tuple of classes, types, and
   such tuples, a "TypeError" exception is raised.

   在 2.2 版更改: Support for a tuple of type information was added.

issubclass(class, classinfo)

   如果 *class* 是 *classinfo* 的子类（直接、间接或 *虚拟* 的），则返
   回 true。*classinfo* 可以是类对象的元组，此时 *classinfo* 中的每个
   元素都会被检查。其他情况，会触发 "TypeError" 异常。

   在 2.3 版更改: Support for a tuple of type information was added.

iter(o[, sentinel])

   Return an *iterator* object.  The first argument is interpreted
   very differently depending on the presence of the second argument.
   Without a second argument, *o* must be a collection object which
   supports the iteration protocol (the "__iter__()" method), or it
   must support the sequence protocol (the "__getitem__()" method with
   integer arguments starting at "0").  If it does not support either
   of those protocols, "TypeError" is raised. If the second argument,
   *sentinel*, is given, then *o* must be a callable object.  The
   iterator created in this case will call *o* with no arguments for
   each call to its "next()" method; if the value returned is equal to
   *sentinel*, "StopIteration" will be raised, otherwise the value
   will be returned.

   One useful application of the second form of "iter()" is to read
   lines of a file until a certain line is reached.  The following
   example reads a file until the "readline()" method returns an empty
   string:

      with open('mydata.txt') as fp:
          for line in iter(fp.readline, ''):
              process_line(line)

   2.2 新版功能.

len(s)

   返回对象的长度（元素个数）。实参可以是序列（如 string、bytes、tuple
   、list 或 range 等）或集合（如 dictionary、set 或 frozen set 等）。

class list([iterable])

   Return a list whose items are the same and in the same order as
   *iterable*’s items.  *iterable* may be either a sequence, a
   container that supports iteration, or an iterator object.  If
   *iterable* is already a list, a copy is made and returned, similar
   to "iterable[:]".  For instance, "list('abc')" returns "['a', 'b',
   'c']" and "list( (1, 2, 3) )" returns "[1, 2, 3]".  If no argument
   is given, returns a new empty list, "[]".

   "list" is a mutable sequence type, as documented in Sequence Types
   — str, unicode, list, tuple, bytearray, buffer, xrange. For other
   containers see the built in "dict", "set", and "tuple" classes, and
   the "collections" module.

locals()

   Update and return a dictionary representing the current local
   symbol table. Free variables are returned by "locals()" when it is
   called in function blocks, but not in class blocks.

   注解: 不要更改此字典的内容；更改不会影响解释器使用的局部变量或自
     由变量 的值。

class long(x=0)
class long(x, base=10)

   Return a long integer object constructed from a string or number
   *x*. If the argument is a string, it must contain a possibly signed
   number of arbitrary size, possibly embedded in whitespace. The
   *base* argument is interpreted in the same way as for "int()", and
   may only be given when *x* is a string. Otherwise, the argument may
   be a plain or long integer or a floating point number, and a long
   integer with the same value is returned.    Conversion of floating
   point numbers to integers truncates (towards zero).  If no
   arguments are given, returns "0L".

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

map(function, iterable, ...)

   Apply *function* to every item of *iterable* and return a list of
   the results. If additional *iterable* arguments are passed,
   *function* must take that many arguments and is applied to the
   items from all iterables in parallel.  If one iterable is shorter
   than another it is assumed to be extended with "None" items.  If
   *function* is "None", the identity function is assumed; if there
   are multiple arguments, "map()" returns a list consisting of tuples
   containing the corresponding items from all iterables (a kind of
   transpose operation).  The *iterable* arguments may be a sequence
   or any iterable object; the result is always a list.

max(iterable[, key])
max(arg1, arg2, *args[, key])

   返回可迭代对象中最大的元素，或者返回两个及以上实参中最大的。

   If one positional argument is provided, *iterable* must be a non-
   empty iterable (such as a non-empty string, tuple or list).  The
   largest item in the iterable is returned.  If two or more
   positional arguments are provided, the largest of the positional
   arguments is returned.

   The optional *key* argument specifies a one-argument ordering
   function like that used for "list.sort()".  The *key* argument, if
   supplied, must be in keyword form (for example,
   "max(a,b,c,key=func)").

   在 2.5 版更改: Added support for the optional *key* argument.

memoryview(obj)

   返回由给定实参创建的“内存视图”对象。有关详细信息，请参阅 memoryview
   type。

min(iterable[, key])
min(arg1, arg2, *args[, key])

   返回可迭代对象中最小的元素，或者返回两个及以上实参中最小的。

   If one positional argument is provided, *iterable* must be a non-
   empty iterable (such as a non-empty string, tuple or list).  The
   smallest item in the iterable is returned.  If two or more
   positional arguments are provided, the smallest of the positional
   arguments is returned.

   The optional *key* argument specifies a one-argument ordering
   function like that used for "list.sort()".  The *key* argument, if
   supplied, must be in keyword form (for example,
   "min(a,b,c,key=func)").

   在 2.5 版更改: Added support for the optional *key* argument.

next(iterator[, default])

   Retrieve the next item from the *iterator* by calling its "next()"
   method.  If *default* is given, it is returned if the iterator is
   exhausted, otherwise "StopIteration" is raised.

   2.6 新版功能.

class object

   Return a new featureless object.  "object" is a base for all new
   style classes.  It has the methods that are common to all instances
   of new style classes.

   2.2 新版功能.

   在 2.3 版更改: This function does not accept any arguments.
   Formerly, it accepted arguments but ignored them.

oct(x)

   Convert an integer number (of any size) to an octal string.  The
   result is a valid Python expression.

   在 2.4 版更改: Formerly only returned an unsigned literal.

open(name[, mode[, buffering]])

   Open a file, returning an object of the "file" type described in
   section File Objects.  If the file cannot be opened, "IOError" is
   raised.  When opening a file, it’s preferable to use "open()"
   instead of invoking the "file" constructor directly.

   The first two arguments are the same as for "stdio"’s "fopen()":
   *name* is the file name to be opened, and *mode* is a string
   indicating how the file is to be opened.

   The most commonly-used values of *mode* are "'r'" for reading,
   "'w'" for writing (truncating the file if it already exists), and
   "'a'" for appending (which on *some* Unix systems means that *all*
   writes append to the end of the file regardless of the current seek
   position).  If *mode* is omitted, it defaults to "'r'".  The
   default is to use text mode, which may convert "'\n'" characters to
   a platform-specific representation on writing and back on reading.
   Thus, when opening a binary file, you should append "'b'" to the
   *mode* value to open the file in binary mode, which will improve
   portability.  (Appending "'b'" is useful even on systems that don’t
   treat binary and text files differently, where it serves as
   documentation.)  See below for more possible values of *mode*.

   The optional *buffering* argument specifies the file’s desired
   buffer size: 0 means unbuffered, 1 means line buffered, any other
   positive value means use a buffer of (approximately) that size (in
   bytes).  A negative *buffering* means to use the system default,
   which is usually line buffered for tty devices and fully buffered
   for other files.  If omitted, the system default is used. [2]

   Modes "'r+'", "'w+'" and "'a+'" open the file for updating (reading
   and writing); note that "'w+'" truncates the file.  Append "'b'" to
   the mode to open the file in binary mode, on systems that
   differentiate between binary and text files; on systems that don’t
   have this distinction, adding the "'b'" has no effect.

   In addition to the standard "fopen()" values *mode* may be "'U'" or
   "'rU'".  Python is usually built with *universal newlines* support;
   supplying "'U'" opens the file as a text file, but lines may be
   terminated by any of the following: the Unix end-of-line convention
   "'\n'",  the Macintosh convention "'\r'", or the Windows convention
   "'\r\n'". All of these external representations are seen as "'\n'"
   by the Python program. If Python is built without universal
   newlines support a *mode* with "'U'" is the same as normal text
   mode.  Note that file objects so opened also have an attribute
   called "newlines" which has a value of "None" (if no newlines have
   yet been seen), "'\n'", "'\r'", "'\r\n'", or a tuple containing all
   the newline types seen.

   Python enforces that the mode, after stripping "'U'", begins with
   "'r'", "'w'" or "'a'".

   Python provides many file handling modules including "fileinput",
   "os", "os.path", "tempfile", and "shutil".

   在 2.5 版更改: Restriction on first letter of mode string
   introduced.

ord(c)

   Given a string of length one, return an integer representing the
   Unicode code point of the character when the argument is a unicode
   object, or the value of the byte when the argument is an 8-bit
   string. For example, "ord('a')" returns the integer "97",
   "ord(u'\u2020')" returns "8224".  This is the inverse of "chr()"
   for 8-bit strings and of "unichr()" for unicode objects.  If a
   unicode argument is given and Python was built with UCS2 Unicode,
   then the character’s code point must be in the range [0..65535]
   inclusive; otherwise the string length is two, and a "TypeError"
   will be raised.

pow(x, y[, z])

   返回 *x* 的 *y* 次幂；如果 *z* 存在，则对 *z* 取余（比直接 "pow(x,
   y) % z" 计算更高效）。两个参数形式的 "pow(x, y)" 等价于幂运算符：
   "x**y"。

   The arguments must have numeric types.  With mixed operand types,
   the coercion rules for binary arithmetic operators apply.  For int
   and long int operands, the result has the same type as the operands
   (after coercion) unless the second argument is negative; in that
   case, all arguments are converted to float and a float result is
   delivered.  For example, "10**2" returns "100", but "10**-2"
   returns "0.01".  (This last feature was added in Python 2.2.  In
   Python 2.1 and before, if both arguments were of integer types and
   the second argument was negative, an exception was raised.) If the
   second argument is negative, the third argument must be omitted. If
   *z* is present, *x* and *y* must be of integer types, and *y* must
   be non-negative.  (This restriction was added in Python 2.2.  In
   Python 2.1 and before, floating 3-argument "pow()" returned
   platform-dependent results depending on floating-point rounding
   accidents.)

print(*objects, sep=' ', end='\n', file=sys.stdout)

   Print *objects* to the stream *file*, separated by *sep* and
   followed by *end*.  *sep*, *end* and *file*, if present, must be
   given as keyword arguments.

   所有非关键字参数都会被转换为字符串，就像是执行了 "str()" 一样，并会
   被写入到流，以 *sep* 且在末尾加上 *end*。 *sep* 和 *end* 都必须为字
   符串；它们也可以为 "None"，这意味着使用默认值。 如果没有给出
   *objects*，则 "print()" 将只写入 *end*。

   The *file* argument must be an object with a "write(string)"
   method; if it is not present or "None", "sys.stdout" will be used.
   Output buffering is determined by *file*.  Use "file.flush()" to
   ensure, for instance, immediate appearance on a screen.

   注解: This function is not normally available as a built-in since
     the name "print" is recognized as the "print" statement.  To
     disable the statement and use the "print()" function, use this
     future statement at the top of your module:

        from __future__ import print_function

   2.6 新版功能.

class property([fget[, fset[, fdel[, doc]]]])

   Return a property attribute for *new-style class*es (classes that
   derive from "object").

   *fget* 是获取属性值的函数。 *fset* 是用于设置属性值的函数。 *fdel*
   是用于删除属性值的函数。并且 *doc* 为属性对象创建文档字符串。

   一个典型的用法是定义一个托管属性 "x":

      class C(object):
          def __init__(self):
              self._x = None

          def getx(self):
              return self._x

          def setx(self, value):
              self._x = value

          def delx(self):
              del self._x

          x = property(getx, setx, delx, "I'm the 'x' property.")

   如果 *c* 是 *C* 的实例，"c.x" 将调用getter，"c.x = value" 将调用
   setter， "del c.x" 将调用deleter。

   如果给出，*doc* 将成为该 property 属性的文档字符串。 否则该
   property 将拷贝 *fget* 的文档字符串（如果存在）。 这令使用
   "property()" 作为 *decorator* 来创建只读的特征属性可以很容易地实现:

      class Parrot(object):
          def __init__(self):
              self._voltage = 100000

          @property
          def voltage(self):
              """Get the current voltage."""
              return self._voltage

   以上 "@property" 装饰器会将 "voltage()" 方法转化为一个具有相同名称
   的只读属性的 “getter”，并将 *voltage* 的文档字符串设置为 “Get the
   current voltage.”

   特征属性对象具有 "getter", "setter" 以及 "deleter" 方法，它们可用作
   装饰器来创建该特征属性的副本，并将相应的访问函数设为所装饰的函数。
   这最好是用一个例子来解释:

      class C(object):
          def __init__(self):
              self._x = None

          @property
          def x(self):
              """I'm the 'x' property."""
              return self._x

          @x.setter
          def x(self, value):
              self._x = value

          @x.deleter
          def x(self):
              del self._x

   上述代码与第一个例子完全等价。 注意一定要给附加函数与原始的特征属性
   相同的名称 (在本例中为 "x"。)

   返回的特征属性对象同样具有与构造器参数相对应的属性 "fget", "fset"
   和 "fdel"。

   2.2 新版功能.

   在 2.5 版更改: Use *fget*’s docstring if no *doc* given.

   在 2.6 版更改: The "getter", "setter", and "deleter" attributes
   were added.

range(stop)
range(start, stop[, step])

   This is a versatile function to create lists containing arithmetic
   progressions. It is most often used in "for" loops.  The arguments
   must be plain integers.  If the *step* argument is omitted, it
   defaults to "1".  If the *start* argument is omitted, it defaults
   to "0".  The full form returns a list of plain integers "[start,
   start + step, start + 2 * step, ...]".  If *step* is positive, the
   last element is the largest "start + i * step" less than *stop*; if
   *step* is negative, the last element is the smallest "start + i *
   step" greater than *stop*.  *step* must not be zero (or else
   "ValueError" is raised).  Example:

   >>> range(10)
   [0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
   >>> range(1, 11)
   [1, 2, 3, 4, 5, 6, 7, 8, 9, 10]
   >>> range(0, 30, 5)
   [0, 5, 10, 15, 20, 25]
   >>> range(0, 10, 3)
   [0, 3, 6, 9]
   >>> range(0, -10, -1)
   [0, -1, -2, -3, -4, -5, -6, -7, -8, -9]
   >>> range(0)
   []
   >>> range(1, 0)
   []

raw_input([prompt])

   If the *prompt* argument is present, it is written to standard
   output without a trailing newline.  The function then reads a line
   from input, converts it to a string (stripping a trailing newline),
   and returns that. When EOF is read, "EOFError" is raised. Example:

      >>> s = raw_input('--> ')
      --> Monty Python's Flying Circus
      >>> s
      "Monty Python's Flying Circus"

   If the "readline" module was loaded, then "raw_input()" will use it
   to provide elaborate line editing and history features.

reduce(function, iterable[, initializer])

   Apply *function* of two arguments cumulatively to the items of
   *iterable*, from left to right, so as to reduce the iterable to a
   single value.  For example, "reduce(lambda x, y: x+y, [1, 2, 3, 4,
   5])" calculates "((((1+2)+3)+4)+5)". The left argument, *x*, is the
   accumulated value and the right argument, *y*, is the update value
   from the *iterable*.  If the optional *initializer* is present, it
   is placed before the items of the iterable in the calculation, and
   serves as a default when the iterable is empty.  If *initializer*
   is not given and *iterable* contains only one item, the first item
   is returned. Roughly equivalent to:

      def reduce(function, iterable, initializer=None):
          it = iter(iterable)
          if initializer is None:
              try:
                  initializer = next(it)
              except StopIteration:
                  raise TypeError('reduce() of empty sequence with no initial value')
          accum_value = initializer
          for x in it:
              accum_value = function(accum_value, x)
          return accum_value

reload(module)

   Reload a previously imported *module*.  The argument must be a
   module object, so it must have been successfully imported before.
   This is useful if you have edited the module source file using an
   external editor and want to try out the new version without leaving
   the Python interpreter.  The return value is the module object (the
   same as the *module* argument).

   When "reload(module)" is executed:

   * Python modules’ code is recompiled and the module-level code
     reexecuted, defining a new set of objects which are bound to
     names in the module’s dictionary.  The "init" function of
     extension modules is not called a second time.

   * As with all other objects in Python the old objects are only
     reclaimed after their reference counts drop to zero.

   * The names in the module namespace are updated to point to any
     new or changed objects.

   * Other references to the old objects (such as names external to
     the module) are not rebound to refer to the new objects and must
     be updated in each namespace where they occur if that is desired.

   There are a number of other caveats:

   When a module is reloaded, its dictionary (containing the module’s
   global variables) is retained.  Redefinitions of names will
   override the old definitions, so this is generally not a problem.
   If the new version of a module does not define a name that was
   defined by the old version, the old definition remains.  This
   feature can be used to the module’s advantage if it maintains a
   global table or cache of objects — with a "try" statement it can
   test for the table’s presence and skip its initialization if
   desired:

      try:
          cache
      except NameError:
          cache = {}

   It is generally not very useful to reload built-in or dynamically
   loaded modules.  Reloading "sys", "__main__", "builtins" and other
   key modules is not recommended.  In many cases extension modules
   are not designed to be initialized more than once, and may fail in
   arbitrary ways when reloaded.

   If a module imports objects from another module using "from" …
   "import" …, calling "reload()" for the other module does not
   redefine the objects imported from it — one way around this is to
   re-execute the "from" statement, another is to use "import" and
   qualified names (*module*.*name*) instead.

   If a module instantiates instances of a class, reloading the module
   that defines the class does not affect the method definitions of
   the instances — they continue to use the old class definition.  The
   same is true for derived classes.

repr(object)

   Return a string containing a printable representation of an object.
   This is the same value yielded by conversions (reverse quotes).  It
   is sometimes useful to be able to access this operation as an
   ordinary function.  For many types, this function makes an attempt
   to return a string that would yield an object with the same value
   when passed to "eval()", otherwise the representation is a string
   enclosed in angle brackets that contains the name of the type of
   the object together with additional information often including the
   name and address of the object.  A class can control what this
   function returns for its instances by defining a "__repr__()"
   method.

reversed(seq)

   返回一个反向的 *iterator*。 *seq* 必须是一个具有 "__reversed__()"
   方法的对象或者是支持该序列协议（具有从 "0" 开始的整数类型参数的
   "__len__()" 方法和 "__getitem__()" 方法）。

   2.4 新版功能.

   在 2.6 版更改: Added the possibility to write a custom
   "__reversed__()" method.

round(number[, ndigits])

   Return the floating point value *number* rounded to *ndigits*
   digits after the decimal point.  If *ndigits* is omitted, it
   defaults to zero. The result is a floating point number.  Values
   are rounded to the closest multiple of 10 to the power minus
   *ndigits*; if two multiples are equally close, rounding is done
   away from 0 (so, for example, "round(0.5)" is "1.0" and
   "round(-0.5)" is "-1.0").

   注解: 对浮点数执行 "round()" 的行为可能会令人惊讶：例如，
     "round(2.675, 2)" 将给出 "2.67" 而不是期望的 "2.68"。 这不算是程
     序错误：这一结 果是由于大多数十进制小数实际上都不能以浮点数精确地
     表示。 请参阅 浮点算术：争议和限制 了解更多信息。

class set([iterable])

   返回一个新的 "set" 对象，可以选择带有从 *iterable* 获取的元素。
   "set" 是一个内置类型。 请查看 "set" 和 集合类型 — set, frozenset 获
   取关于这个类的文档。

   有关其他容器请参看内置的 "frozenset", "list", "tuple" 和 "dict" 类
   ，以及 "collections" 模块。

   2.4 新版功能.

setattr(object, name, value)

   此函数与 "getattr()" 两相对应。 其参数为一个对象、一个字符串和一个
   任意值。 字符串指定一个现有属性或者新增属性。 函数会将值赋给该属性
   ，只要对象允许这种操作。 例如，"setattr(x, 'foobar', 123)" 等价于
   "x.foobar = 123"。

class slice(stop)
class slice(start, stop[, step])

   返回一个表示由 "range(start, stop, step)" 所指定索引集的 *slice* 对
   象。 其中 *start* 和 *step* 参数默认为 "None"。 切片对象具有仅会返
   回对应参数值（或其默认值）的只读数据属性 "start", "stop" 和 "step"
   。 它们没有其他的显式功能；不过它们会被 NumPy 以及其他第三方扩展所
   使用。 切片对象也会在使用扩展索引语法时被生成。 例如:
   "a[start:stop:step]" 或 "a[start:stop, i]"。 请参阅
   "itertools.islice()" 了解返回迭代器的一种替代版本。

sorted(iterable[, cmp[, key[, reverse]]])

   根据 *iterable* 中的项返回一个新的已排序列表。

   The optional arguments *cmp*, *key*, and *reverse* have the same
   meaning as those for the "list.sort()" method (described in section
   可变序列类型).

   *cmp* specifies a custom comparison function of two arguments
   (iterable elements) which should return a negative, zero or
   positive number depending on whether the first argument is
   considered smaller than, equal to, or larger than the second
   argument: "cmp=lambda x,y: cmp(x.lower(), y.lower())".  The default
   value is "None".

   *key* specifies a function of one argument that is used to extract
   a comparison key from each list element: "key=str.lower".  The
   default value is "None" (compare the elements directly).

   *reverse* 为一个布尔值。 如果设为 "True"，则每个列表元素将按反向顺
   序比较进行排序。

   In general, the *key* and *reverse* conversion processes are much
   faster than specifying an equivalent *cmp* function.  This is
   because *cmp* is called multiple times for each list element while
   *key* and *reverse* touch each element only once.  Use
   "functools.cmp_to_key()" to convert an old-style *cmp* function to
   a *key* function.

   内置的 "sorted()" 确保是稳定的。 如果一个排序确保不会改变比较结果相
   等的元素的相对顺序就称其为稳定的 — 这有利于进行多重排序（例如先按部
   门、再按薪级排序）。

   有关排序示例和简要排序教程，请参阅 排序指南 。

   2.4 新版功能.

staticmethod(function)

   Return a static method for *function*.

   静态方法不会接收隐式的第一个参数。要声明一个静态方法，请使用此语法

      class C(object):
          @staticmethod
          def f(arg1, arg2, ...):
              ...

   "@staticmethod" 这样的形式称为函数的 *decorator* – 详情参阅 函数定
   义。

   静态方法的调用可以在类上进行 (例如 "C.f()") 也可以在实例上进行 (例
   如 "C().f()")。

   Python中的静态方法与Java或C ++中的静态方法类似。另请参阅
   "classmethod()" ，用于创建备用类构造函数的变体。

   想了解更多有关静态方法的信息，请参阅 标准类型层级结构 。

   2.2 新版功能.

   在 2.4 版更改: Function decorator syntax added.

class str(object='')

   Return a string containing a nicely printable representation of an
   object.  For strings, this returns the string itself.  The
   difference with "repr(object)" is that "str(object)" does not
   always attempt to return a string that is acceptable to "eval()";
   its goal is to return a printable string.  If no argument is given,
   returns the empty string, "''".

   For more information on strings see Sequence Types — str, unicode,
   list, tuple, bytearray, buffer, xrange which describes sequence
   functionality (strings are sequences), and also the string-specific
   methods described in the 字符串的方法 section. To output formatted
   strings use template strings or the "%" operator described in the
   String Formatting Operations section. In addition see the String
   Services section. See also "unicode()".

sum(iterable[, start])

   从 *start* 开始自左向右对 *iterable* 中的项求和并返回总计值。
   *start* 默认为 "0"。 *iterable* 的项通常为数字，开始值则不允许为字
   符串。

   对某些用例来说，存在 "sum()" 的更好替代。 拼接字符串序列的更好更快
   方式是调用 "''.join(sequence)"。 要以扩展精度对浮点值求和，请参阅
   "math.fsum()"。 要拼接一系列可迭代对象，请考虑使用
   "itertools.chain()"。

   2.3 新版功能.

super(type[, object-or-type])

   返回一个代理对象，它会将方法调用委托给 *type* 指定的父类或兄弟类。
   这对于访问已在类中被重载的继承方法很有用。 搜索顺序与 "getattr()"
   所使用的相同，只是 *type* 指定的类型本身会被跳过。

   *type* 的 "__mro__" 属性列出了 "getattr()" 和 "super()" 所使用的方
   法解析顺序。 该属性是动态的，可以在继承层级结构更新的时候任意改变。

   如果省略第二个参数，则返回的超类对象是未绑定的。 如果第二个参数为一
   个对象，则 "isinstance(obj, type)" 必须为真值。 如果第二个参数为一
   个类型，则 "issubclass(type2, type)" 必须为真值（这适用于类方法）。

   注解: "super()" only works for *new-style class*es.

   *super* 有两个典型用例。 在具有单继承的类层级结构中，*super* 可用来
   引用父类而不必显式地指定它们的名称，从而令代码更易维护。 这种用法与
   其他编程语言中 *super* 的用法非常相似。

   第二个用例是在动态执行环境中支持协作多重继承。 此用例为 Python 所独
   有，在静态编译语言或仅支持单继承的语言中是不存在的。 这使得实现“菱
   形图”成为可能，在这时会有多个基类实现相同的方法。 好的设计强制要求
   这种方法在每个情况下具有相同的调用签名（因为调用顺序是在运行时确定
   的，也因为该顺序要适应类层级结构的更改，还因为该顺序可能包含在运行
   时之前未知的兄弟类）。

   对于以上两个用例，典型的超类调用看起来是这样的:

      class C(B):
          def method(self, arg):
              super(C, self).method(arg)

   请注意 "super()" 是作为显式加点属性查找的绑定过程的一部分来实现的，
   例如 "super().__getitem__(name)"。 它做到这一点是通过实现自己的
   "__getattribute__()" 方法，这样就能以可预测的顺序搜索类，并且支持协
   作多重继承。 对应地，"super()" 在像 "super()[name]" 这样使用语句或
   操作符进行隐式查找时则未被定义。

   Also note that "super()" is not limited to use inside methods.  The
   two argument form specifies the arguments exactly and makes the
   appropriate references.

   对于有关如何使用 "super()" 来如何设计协作类的实用建议，请参阅 使用
   super() 的指南。

   2.2 新版功能.

tuple([iterable])

   Return a tuple whose items are the same and in the same order as
   *iterable*’s items.  *iterable* may be a sequence, a container that
   supports iteration, or an iterator object. If *iterable* is already
   a tuple, it is returned unchanged. For instance, "tuple('abc')"
   returns "('a', 'b', 'c')" and "tuple([1, 2, 3])" returns "(1, 2,
   3)".  If no argument is given, returns a new empty tuple, "()".

   "tuple" is an immutable sequence type, as documented in Sequence
   Types — str, unicode, list, tuple, bytearray, buffer, xrange. For
   other containers see the built in "dict", "list", and "set"
   classes, and the "collections" module.

class type(object)
class type(name, bases, dict)

   With one argument, return the type of an *object*.  The return
   value is a type object.  The "isinstance()" built-in function is
   recommended for testing the type of an object.

   With three arguments, return a new type object.  This is
   essentially a dynamic form of the "class" statement. The *name*
   string is the class name and becomes the "__name__" attribute; the
   *bases* tuple itemizes the base classes and becomes the "__bases__"
   attribute; and the *dict* dictionary is the namespace containing
   definitions for class body and becomes the "__dict__"  attribute.
   For example, the following two statements create identical "type"
   objects:

   >>> class X(object):
   ...     a = 1
   ...
   >>> X = type('X', (object,), dict(a=1))

   2.2 新版功能.

unichr(i)

   Return the Unicode string of one character whose Unicode code is
   the integer *i*.  For example, "unichr(97)" returns the string
   "u'a'".  This is the inverse of "ord()" for Unicode strings.  The
   valid range for the argument depends how Python was configured – it
   may be either UCS2 [0..0xFFFF] or UCS4 [0..0x10FFFF]. "ValueError"
   is raised otherwise. For ASCII and 8-bit strings see "chr()".

   2.0 新版功能.

unicode(object='')
unicode(object[, encoding[, errors]])

   Return the Unicode string version of *object* using one of the
   following modes:

   If *encoding* and/or *errors* are given, "unicode()" will decode
   the object which can either be an 8-bit string or a character
   buffer using the codec for *encoding*. The *encoding* parameter is
   a string giving the name of an encoding; if the encoding is not
   known, "LookupError" is raised. Error handling is done according to
   *errors*; this specifies the treatment of characters which are
   invalid in the input encoding.  If *errors* is "'strict'" (the
   default), a "ValueError" is raised on errors, while a value of
   "'ignore'" causes errors to be silently ignored, and a value of
   "'replace'" causes the official Unicode replacement character,
   "U+FFFD", to be used to replace input characters which cannot be
   decoded.  See also the "codecs" module.

   If no optional parameters are given, "unicode()" will mimic the
   behaviour of "str()" except that it returns Unicode strings instead
   of 8-bit strings. More precisely, if *object* is a Unicode string
   or subclass it will return that Unicode string without any
   additional decoding applied.

   For objects which provide a "__unicode__()" method, it will call
   this method without arguments to create a Unicode string. For all
   other objects, the 8-bit string version or representation is
   requested and then converted to a Unicode string using the codec
   for the default encoding in "'strict'" mode.

   For more information on Unicode strings see Sequence Types — str,
   unicode, list, tuple, bytearray, buffer, xrange which describes
   sequence functionality (Unicode strings are sequences), and also
   the string-specific methods described in the 字符串的方法 section.
   To output formatted strings use template strings or the "%"
   operator described in the String Formatting Operations section. In
   addition see the String Services section. See also "str()".

   2.0 新版功能.

   在 2.2 版更改: Support for "__unicode__()" added.

vars([object])

   返回模块、类、实例或任何其它具有 "__dict__" 属性的对象的 "__dict__"
   属性。

   Objects such as modules and instances have an updateable "__dict__"
   attribute; however, other objects may have write restrictions on
   their "__dict__" attributes (for example, new-style classes use a
   dictproxy to prevent direct dictionary updates).

   不带参数时，"vars()" 的行为类似 "locals()"。 请注意，locals 字典仅
   对于读取起作用，因为对 locals 字典的更新会被忽略。

xrange(stop)
xrange(start, stop[, step])

   This function is very similar to "range()", but returns an xrange
   object instead of a list.  This is an opaque sequence type which
   yields the same values as the corresponding list, without actually
   storing them all simultaneously. The advantage of "xrange()" over
   "range()" is minimal (since "xrange()" still has to create the
   values when asked for them) except when a very large range is used
   on a memory-starved machine or when all of the range’s elements are
   never used (such as when the loop is usually terminated with
   "break").  For more information on xrange objects, see XRange Type
   and Sequence Types — str, unicode, list, tuple, bytearray, buffer,
   xrange.

   **CPython implementation detail:** "xrange()" is intended to be
   simple and fast.  Implementations may impose restrictions to
   achieve this.  The C implementation of Python restricts all
   arguments to native C longs (“short” Python integers), and also
   requires that the number of elements fit in a native C long.  If a
   larger range is needed, an alternate version can be crafted using
   the "itertools" module: "islice(count(start, step), (stop-
   start+step-1+2*(step<0))//step)".

zip([iterable, ...])

   This function returns a list of tuples, where the *i*-th tuple
   contains the *i*-th element from each of the argument sequences or
   iterables. The returned list is truncated in length to the length
   of the shortest argument sequence. When there are multiple
   arguments which are all of the same length, "zip()" is similar to
   "map()" with an initial argument of "None". With a single sequence
   argument, it returns a list of 1-tuples. With no arguments, it
   returns an empty list.

   The left-to-right evaluation order of the iterables is guaranteed.
   This makes possible an idiom for clustering a data series into
   n-length groups using "zip(*[iter(s)]*n)".

   "zip()" 与 "*" 运算符相结合可以用来拆解一个列表:

      >>> x = [1, 2, 3]
      >>> y = [4, 5, 6]
      >>> zipped = zip(x, y)
      >>> zipped
      [(1, 4), (2, 5), (3, 6)]
      >>> x2, y2 = zip(*zipped)
      >>> x == list(x2) and y == list(y2)
      True

   2.0 新版功能.

   在 2.4 版更改: Formerly, "zip()" required at least one argument and
   "zip()" raised a "TypeError" instead of returning an empty list.

__import__(name[, globals[, locals[, fromlist[, level]]]])

   注解: 与 "importlib.import_module()" 不同，这是一个日常 Python 编
     程中不 需要用到的高级函数。

   This function is invoked by the "import" statement.  It can be
   replaced (by importing the "__builtin__" module and assigning to
   "__builtin__.__import__") in order to change semantics of the
   "import" statement, but nowadays it is usually simpler to use
   import hooks (see **PEP 302**).  Direct use of "__import__()" is
   rare, except in cases where you want to import a module whose name
   is only known at runtime.

   该函数会导入 *name* 模块，有可能使用给定的 *globals* 和 *locals* 来
   确定如何在包的上下文中解读名称。 *fromlist* 给出了应该从由 *name*
   指定的模块导入对象或子模块的名称。 标准实现完全不使用其 *locals* 参
   数，而仅使用 *globals* 参数来确定 "import" 语句的包上下文。

   *level* specifies whether to use absolute or relative imports.  The
   default is "-1" which indicates both absolute and relative imports
   will be attempted.  "0" means only perform absolute imports.
   Positive values for *level* indicate the number of parent
   directories to search relative to the directory of the module
   calling "__import__()".

   当 *name* 变量的形式为 "package.module" 时，通常将会返回最高层级的
   包（第一个点号之前的名称），而 *不是* 以 *name* 命名的模块。 但是，
   当给出了非空的 *fromlist* 参数时，则将返回以 *name* 命名的模块。

   例如，语句 "import spam" 的结果将为与以下代码作用相同的字节码:

      spam = __import__('spam', globals(), locals(), [], -1)

   语句 "import spam.ham" 的结果将为以下调用:

      spam = __import__('spam.ham', globals(), locals(), [], -1)

   请注意在这里 "__import__()" 是如何返回顶层模块的，因为这是通过
   "import" 语句被绑定到特定名称的对象。

   另一方面，语句 "from spam.ham import eggs, sausage as saus" 的结果
   将为

      _temp = __import__('spam.ham', globals(), locals(), ['eggs', 'sausage'], -1)
      eggs = _temp.eggs
      saus = _temp.sausage

   在这里， "spam.ham" 模块会由 "__import__()" 返回。 要导入的对象将从
   此对象中提取并赋值给它们对应的名称。

   如果您只想按名称导入模块（可能在包中），请使用
   "importlib.import_module()"

   在 2.5 版更改: The level parameter was added.

   在 2.5 版更改: Keyword support for parameters was added.


3. Non-essential Built-in Functions
***********************************

There are several built-in functions that are no longer essential to
learn, know or use in modern Python programming.  They have been kept
here to maintain backwards compatibility with programs written for
older versions of Python.

Python programmers, trainers, students and book writers should feel
free to bypass these functions without concerns about missing
something important.

apply(function, args[, keywords])

   The *function* argument must be a callable object (a user-defined
   or built-in function or method, or a class object) and the *args*
   argument must be a sequence.  The *function* is called with *args*
   as the argument list; the number of arguments is the length of the
   tuple. If the optional *keywords* argument is present, it must be a
   dictionary whose keys are strings.  It specifies keyword arguments
   to be added to the end of the argument list. Calling "apply()" is
   different from just calling "function(args)", since in that case
   there is always exactly one argument.  The use of "apply()" is
   equivalent to "function(*args, **keywords)".

   2.3 版后已移除: Use "function(*args, **keywords)" instead of
   "apply(function, args, keywords)" (see 解包参数列表).

buffer(object[, offset[, size]])

   The *object* argument must be an object that supports the buffer
   call interface (such as strings, arrays, and buffers).  A new
   buffer object will be created which references the *object*
   argument. The buffer object will be a slice from the beginning of
   *object* (or from the specified *offset*). The slice will extend to
   the end of *object* (or will have a length given by the *size*
   argument).

coerce(x, y)

   Return a tuple consisting of the two numeric arguments converted to
   a common type, using the same rules as used by arithmetic
   operations. If coercion is not possible, raise "TypeError".

intern(string)

   Enter *string* in the table of “interned” strings and return the
   interned string – which is *string* itself or a copy. Interning
   strings is useful to gain a little performance on dictionary lookup
   – if the keys in a dictionary are interned, and the lookup key is
   interned, the key comparisons (after hashing) can be done by a
   pointer compare instead of a string compare.  Normally, the names
   used in Python programs are automatically interned, and the
   dictionaries used to hold module, class or instance attributes have
   interned keys.

   在 2.3 版更改: Interned strings are not immortal (like they used to
   be in Python 2.2 and before); you must keep a reference to the
   return value of "intern()" around to benefit from it.

-[ 备注 ]-

[1] It is used relatively rarely so does not warrant being made
    into a statement.

[2] Specifying a buffer size currently has no effect on systems
    that don’t have "setvbuf()".  The interface to specify the buffer
    size is not done using a method that calls "setvbuf()", because
    that may dump core when called after any I/O has been performed,
    and there’s no reliable way to determine whether this is the case.

[3] In the current implementation, local variable bindings cannot
    normally be affected this way, but variables retrieved from other
    scopes (such as modules) can be.  This may change.
