common letters in two strings

Question

I\'ve been trying to solve this program which takes two strings as input and outputs number of common letters. For Example, if the input was \"common\" and \"connor\" then t

Answer 1

Use collections.Counter:

>>> from collections import Counter

>>> Counter('common')
Counter({'m': 2, 'o': 2, 'c': 1, 'n': 1})
>>> Counter('connor')
Counter({'o': 2, 'n': 2, 'c': 1, 'r': 1})

>>> common = Counter('common') & Counter('connor') # intersection
>>> common
Counter({'o': 2, 'c': 1, 'n': 1})
>>> sum(common.values())
4

Answer 2

you can do list comprehension for that too

>>> a = 'common'
>>> b = 'connor'
>>> sum([1 for l in a if l in b])
4

EDIT

a,b = 'come','common'

def collision_count(a,b):
    da = {l:a.count(l) for l in a}
    db = {l:b.count(l) for l in b}
    return sum(min(v,db[k]) for k,v in da.items() if k in db.keys())

print collision_count(a,b)
3

Are you now ok with that?