Decrypts the python id () function

Source: Internet
Author: User

>>> A = 2.5
>>> B = 2.5
>>> C = B
>>> A is c
False
>>> A = 2
>>> B = 2
>>> C = B
>>> A is c
True
When I use the is function today, I print the numbers a and B are assigned 2.5 and 2 respectively. I found that:
>>> A = 2
>>> B = 2
>>> Id ()
21132060
>>> Id (B)
21132060
>>> A = 2.5
>>> B = 2.5
>>> Id ()
19622112
>>> Id (B)
29321464
When a and B are 2, the id is the same, but 2.5 is different. This problem also occurs when the string is short, when B is assigned a very short string, their IDs are the same, but long strings do not;
Change
Then, we can get a simple conclusion: the interpreter makes a small Optimization for int and short strings with a small value, and only allocates one object, let them have the same id.

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