python内置函数1-bin()

Help on built-in function bin in module __builtin__:

bin(...)

    bin(number) -> string

    Return the binary representation of an integer or long integer.

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.

说明：将整数x转换为二进制字符串，如果x不为Python中int类型，x必须包含方法__index__()并且返回值为integer；

参数x：整数或者包含__index__()方法切返回值为integer的类型；

>>> bin(123)

‘0b1111011‘

>>> a=bin(67)

>>> a

‘0b1000011‘

这里的显示结果形式与我们平时习惯有些差别，主要是前面多了0b，这是表示二进制的意思

如果对象不是整数，则报错

>>> class A:

...     pass

... 

>>> a=A()

>>> bin(a)

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: object cannot be interpreted as an index

如果对象定义了__index__方法，但返回值不是整数，报错

>>> class B:

...     def __index__(self):

...         return "56"

... 

>>> b=B()

>>> bin(b)

Traceback (most recent call last):

  File "<stdin>", line 1, in <module>

TypeError: __index__ returned non-(int,long) (type str)

非整型的情况，必须包含__index__()方法切返回值为integer的类型

>>> class myType:

...     def __index__(self):

...         return 35

... 

>>> myvar=myType()

>>> bin(myvar)

‘0b100011‘

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python内置函数1-bin()

原文：http://hdlptz.blog.51cto.com/12553181/1897559