英文文件：
hex(x)
Convert an integer number to a lowercase hexadecimal string prefixed with “0x”, for example
If x is not a__n ☺ returns an integer.
說明：
1. 函數函數將10進位整數轉換成16進位整數。
>>> hex(15)'0xf'>>> hex(16)'0x10'
2. 如果參數x不是整數，則它必須定義一個傳回整數的__index__函數。
# 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: 'Student' 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('Kim',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('Kim',10)
>>> hex(s)
'0xa'
