python 中 is, is not ,==, != 的区别

首先说结论：

1、is, is not 对比的是两个变量的内存地址

2、==,!= 对比的是两个变量的值

由此可以进一步推出：

a、假如比较的两个变量，指向的都是地址不可变的类型（str等），那么is，is not 和 ==，！= 是完全等价的。

b、假如对比的两个变量，指向的是地址可变的类型（list，dict，tuple等），则两者是有区别的。

示例:

# python code to differentiate between != and “is not” operator.

 

# comparing object with integer datatype

a = 10

b = 10

print("comparison with != operator",a != b)

print("comparison with is not operator ", a is not b)

print(id(a), id(b))

 

# comparing objects with string data type

c = "Python"

d = "Python"

print("comparison with != operator",c != d)

print("comparison with is not operator", c is not d)

print(id(c), id(d))

 

# comparing list

e = [ 1, 2, 3, 4]

f=[ 1, 2, 3, 4]

print("comparison with != operator",e != f)

print("comparison with is not operator", e is not f)

print(id(e), id(f))

comparison with != operator False

comparison with is not operator  False

139927053992464 139927053992464

comparison with != operator False

comparison with is not operator False

139927052823408 139927052823408

comparison with != operator False

comparison with is not operator True

139927054711552 139927052867136