Question

Say we got two lists:

a = [1, 2, 3]
b = [1, 2, 3]

All the following expressions will return True:

a == b  # True
a == list(b) # True
a == list(tuple(b)) # True
a == copy.deepcopy(b) # still True

Here a and b are 2 different list objects with the same elements.
How do we distinguish one from another?

Answer 1

is compares identity. It asks are a and b the same object

>>> a=[1, 2, 3]
>>> b=list(a)
>>> id(a)
3065460108L
>>> id(b)
3073003244L
>>> id(a) == id(b)   # Equivalent to a is b
False
>>> a is b
False