Python Identity Operators

a = [1, 2]
b = [1, 2]
print(id(a) == id(b))  # different objects, so different memory addresses
print(a is b)  # False, they are equal in value but not identical

a = [1, 2]
b = a  # b now refers to the same list object as a
c = [1, 2]  # c is a separate object with equal contents
print(a is b)  # True, same object
print(a is not c)  # True, different objects

x = None
print(x is None)  # idiomatic identity check for None
print(x == None)  # works here too, but is not the recommended style

a = 5
b = 5
print(a is b)  # True due to CPython's small-int caching, not guaranteed behavior

def process(items=None):
    if items is None:
        items = []  # a new list object is created each call
    return items

a = process()
b = process()
print(a is b)  # False, each call got its own list object