Check this example:
class X:
foo = []
q, w = X(), X()
q.foo.append(1)
w.foo
ans: [1]
class X:
def __init__(self):
self.foo = []
q, w = X(), X()
q.foo.append(1)
w.foo
ans: []
Hence, It's clear from above that Self refers to object itself.
Happy Learning...!!