Python built-in functions

English documentation:

hex(x)

Convert an integer number to a lowercase hexadecimal string prefixed with “0x”, for example

If x is not a Python int object, it has to define an __index__() method that returns an integer.

Instructions:

　　1. The function converts a decimal integer into a hexadecimal integer.

>>> hex(15)'0xf'>>> hex(16)'0x10'

　2. If the parameter x is not an integer, it must define an __index__ function that returns an integer.

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

>>> 
>>> s = Student('Kim',10)
>>> hex(s)
Traceback (most recent call last):
  File "<pyshell#17>", line 1, in <module>
    hex(s)
TypeError: &#39;Student&#39; object cannot be interpreted as an integer

# 定义__index__函数，但是返回字符串
>>> class Student:
    def __init__(self,name,age):
        self.name = name
        self.age = age
    def __index__(self):
        return self.name

>>> s = Student(&#39;Kim&#39;,10)
>>> hex(s)
Traceback (most recent call last):
  File "<pyshell#23>", line 1, in <module>
    hex(s)
TypeError: __index__ returned non-int (type str)

# 定义__index__函数，并返回整数
>>> class Student:
    def __init__(self,name,age):
        self.name = name
        self.age = age
    def __index__(self):
        return self.age

>>> s = Student(&#39;Kim&#39;,10)
>>> hex(s)
&#39;0xa&#39;