Python内置函数OCT详解

英文文档：

复制代码 代码如下:

oct ( x )
Convert an integer number to an octal string. The result is a valid Python expression. If x is not a Pythonobject, it has to define anmethod that returns an integer.

说明：

1. 函数功能将一个整数转换成8进制字符串。如果传入浮点数或者字符串均会报错。

    >>> a = oct(10)

    >>> a
    '0o12'
    >>> type(a) # 返回结果类型是字符串
    <class 'str'>

    >>> oct(10.0) # 浮点数不能转换成8进制
    Traceback (most recent call last):
     File "<pyshell#3>", line 1, in <module>
      oct(10.0)
    TypeError: 'float' object cannot be interpreted as an integer

    >>> oct('10') # 字符串不能转换成8进制
    Traceback (most recent call last):
     File "<pyshell#4>", line 1, in <module>
      oct('10')
    TypeError: 'str' object cannot be interpreted as an integer

2. 如果传入参数不是整数，则其必须是一个定义了index并返回整数函数的类的实例对象。

    # 未定义__index__函数，不能转换
    >>> class Student:
      def __init__(self,name,age):
        self.name = name
        self.age = age

    >>> a = Student('Kim',10)
    >>> oct(a)
    Traceback (most recent call last):
     File "<pyshell#12>", line 1, in <module>
      oct(a)
    TypeError: 'Student' object cannot be interpreted as an integer

    # 定义了__index__函数，但是返回值不是int类型，不能转换
    >>> class Student:
      def __init__(self,name,age):
        self.name = name
        self.age = age
      def __index__(self):
        return self.name

    >>> a = Student('Kim',10)
    >>> oct(a)
    Traceback (most recent call last):
     File "<pyshell#18>", line 1, in <module>
      oct(a)
    TypeError: __index__ returned non-int (type str)

    # 定义了__index__函数，而且返回值是int类型，能转换
    >>> class Student:
      def __init__(self,name,age):
        self.name = name
        self.age = age
      def __index__(self):
        return self.age

    >>> a = Student('Kim',10)
    >>> oct(a)
    '0o12'