Variables in Python

Question

Here is a little script:

class Any(object):
    def __init__(self,x):
        self.x=x

l = [Any(2),Any(3),Any(7),Any(9),Any(10)]
print(len(l))
l2=[ind for ind in l]
l3=l
print(set(l2).difference(l3))
print(l2[1]==l[1])
print(l3[1]==l[1])
del l2[1]
print(len(l))
del l3[1]
print(len(l))

Why deleting an instance of Any in l2 doesn't change l, but deleting it in l3changes l although it seems not to have any difference between l2 and l3?

Thanks a lot!

Answer 1

l2 is a different object created from l

l3 refers to the same object as l. So changing anything in l or l3 will affect that object and therefore will affect l and l3.

Answer 2

Because:

>>> l is l2
False
>>> l is l3
True

Binding the reference twice makes both names refer to the same object.