字体：大中小

python中is和==区别

Python　2024/12/7 19:56:39　　点击：不统计

python中有2个判断相等关系的关键词 is 和== 那他们有什么区别吗？看下面代码

# -*- coding: utf-8 -*-
"""INFO"""


a = "ab"
b = "ab"
c = "a" + "b"
d = "".join(['a', "b"])
print(a is b)  # 返回True
print(a == b)  # 返回True
print(a is c)  # True
print(a == c)  # True
print(a == d)  # True
print(a is d)  # False


class D:
    a = None
    b = "ab"


d_obj = D()
print(d_obj.a is None)  # True
print(d_obj.b == c)  # True
print(d_obj.b is b)  # True

d_obj2 = D()
print(d_obj == d_obj2)  # False
print(d_obj is d_obj2)  # False
print(d_obj.b == d_obj2.b)  # True
print(d_obj.b is d_obj2.b)  # True

d_obj2.change = "change"
print(d_obj == d_obj2)  # False
print(d_obj is d_obj2)  # False

总结
is 比较的是 id值，在相同的对象是一致的，不同对象 不一致
== 直接比较的是值, == 号的行为可以在类的 __eq__ 中重载
可以通过 python -m dis xxx.py 运行测试看具体的代码执行编译程序

·上一篇：python中的魔术方法 >> 　　　·下一篇：python 提高性能转换为c语言 >>