# When you've understood the difference between the three methods,
# write a procedure list_test which takes three lists as inputs. You should
# mutate the first input list to include 'a' as the last entry, mutate the
# second to include the entries 'a', 'b', 'c' and finally the last list should
# not be mutated but a copy should be returned with the additional entry 'w'.

first_input = [1,2,3]
second_input = [4,5,6]
third_input = [7,8,9]
a = first_input
b = second_input
c = third_input
#print a
#print b
#print c



def list_test(a,b,c):
    a.append("a")
    b= b + ["a","b","c"]
    d=c+["w"]
    return a,b,d


print "results of procedure", list_test(first_input, second_input, third_input)

#>>> [7,8,9,'w']
print first_input
#>>> [1,2,3,'a']
print second_input
#>>> [4,5,6,'a','b','c']
print third_input
#>>> [7,8,9]