double equals vs is in python [duplicate]

问题:

This question already has an answer here:

• Is there a difference between `==` and `is` in Python? 20 answers
• String comparison in Python: is vs. == [duplicate] 4 answers

I run the following in the Python interpreter:

>>> foo = 10
>>> dir(foo) == dir(10)
True
>>> dir(foo) is dir(10)
False
>>> 

Why is this?

回答1:

is checks that 2 arguments refer to the same object, == checks that 2 arguments have the same value. dir() returns a list which contains the same data for both foo and 10, but the actual list instances for the 2 things are different.