need a good explain for this code, pls :

Question

arr=[1,2]
a=arr
print(a is not arr)
>>> False # ?! it's like value different of var ?
a=list(a)
print(a)
>>> [1,2]
print(a is not arr)
>>> True # ?! why ???

Answer 1

In the first instance, a and arr are pointers to the same object (because of the line a=arr). So a is arr would return True. That is why a is not arr returns False.

For the second instance, a=list(a) means that a is now a copy of the list, not the same one. So here, a is arr will return False, so a is not arr returns True.

You can see this by looking at the id of a variable. a is arr is equivalent to id(a) == id(arr).

Answer 2

thk for answer