The difference between python is and ==

The difference between pythonis and ==:

##is is used to determine two variable references Whether the objects are the same, == is used to determine whether the values ​​of reference variables are equal.

a is b is equivalent to id(a)==id(b), id() can obtain the memory address of the object. (Recommended learning:

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If a=10;b=a; then the memory addresses of a and b are the same at this time;

But when a =[1,2,3]; When b=a[:], although the values ​​of a and b are the same, the memory addresses are different.

If you define a=10, b=10 at this time, and then compare a is b, you will find that the returned result is True. This is because a small shaping pool will be created in Python with a range of [ -5,256] to open up memory space for these integers. When integers within this range are defined in the code, the memory address will not be reallocated.

And I tested it in Pycharm:

#coding=utf-8
a=100000000000;
b=100000000000;
print a is b

The result:

 True

After checking the information, I found out: For performance reasons, Python will not repeatedly create immutable objects in the same code block, but will directly reference existing objects as long as they have the same value.

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