Detailed explanation of Python built-in function OCT

English document:

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.

Instructions:

1. The function converts an integer into an octal string. If you pass in a floating point number or a string, an error will be reported.

>>> a = oct(10)
  
>>> a
'0o12'
>>> type(a) # 返回结果类型是字符串
<class &#39;str&#39;>
  
>>> 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: &#39;float&#39; object cannot be interpreted as an integer
  
>>> oct(&#39;10&#39;) # 字符串不能转换成8进制
Traceback (most recent call last):
 File "<pyshell#4>", line 1, in <module>
  oct(&#39;10&#39;)
TypeError: &#39;str&#39; object cannot be interpreted as an integer

2. If the incoming parameter is not an integer, it must be an instance object of a class that defines __index__ and returns an integer function.

# The __index__ function is not defined and cannot be converted

>>> 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 "", line 1, in

oct(a)

TypeError: 'Student' object cannot be interpreted as an integer

# The __index__ function is defined, but the return value is not int Type, cannot be converted

>>> 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(&#39;Kim&#39;,10)
>>> oct(a)
&#39;0o12&#39;

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