mutable demonstration code

mutable.py

#!/usr/bin/python

import copy

def mutable(myset):
    myset.extend([10,11,12])
    print 'inside mutable function:', myset 

def nonmutable(myset):
    myset = copy.copy(myset)
    myset.extend([10,11,12])
    print 'inside nonmutable function:', myset 

print
print 'Mutable test'
print
ourset = [1, 2, 3, 4, 5, 6]
print 'Our set before calling:', ourset
mutable(ourset)
print 'Our set after calling:', ourset


print
print 'NonMutable test'
print
ourset = [1, 2, 3, 4, 5, 6]
print 'Our set before calling:', ourset
nonmutable(ourset)
print 'Our set after calling:', ourset

output.txt

$ python mutable.py

Mutable test

Our set before calling: [1, 2, 3, 4, 5, 6]
inside mutable function: [1, 2, 3, 4, 5, 6, 10, 11, 12]
Our set after calling: [1, 2, 3, 4, 5, 6, 10, 11, 12]

NonMutable test

Our set before calling: [1, 2, 3, 4, 5, 6]
inside nonmutable function: [1, 2, 3, 4, 5, 6, 10, 11, 12]
Our set after calling: [1, 2, 3, 4, 5, 6]