python copy variable

1>>> import copy
2>>> a = 0
3>>> b = 2
4>>> a = copy.copy(b)
5>>> b += 1
6>>> a
72
8>>> b
93

1s1 = set()
2s2 = s1.copy()

1class Foo:
2    def __init__(self, orig=None):
3        if orig is None:
4            self.non_copy_constructor()
5        else:
6            self.copy_constructor(orig)
7    def non_copy_constructor(self):
8        # do the non-copy constructor stuff
9    def copy_constructor(self, orig):
10        # do the copy constructor
11
12a=Foo()  # this will call the non-copy constructor
13b=Foo(a) # this will call the copy constructor