How to subtract two strings?

Question

I have a long string, which is basically a list like str=\"lamp, bag, mirror,\" (and other items)

I was wondering if I can add or subtract some items, i

Answer 1

from re import sub

def Str2MinusStr1 (str1, str2, n=1) :
    return sub(r'%s' % (str2), '', str1, n)

Str2MinusStr1 ('aabbaa', 'a')  
# result 'abbaa'

Str2MinusStr1 ('aabbaa', 'ab')  
# result 'abaa'

Str2MinusStr1 ('aabbaa', 'a', 0)  
# result 'bb'

# n = number of occurences. 
# 0 means all, else means n of occurences. 
# str2 can be any regular expression. 

Answer 2

Using the following you can add more words to remove (["bag", "mirror", ...])

(s0, to_remove) = ("lamp, bag, mirror", ["bag"])
s0 = ", ".join([x for x in s0.split(", ") if x not in to_remove])
=> "lamp, mirror"