如何在python中优化此代码

Question

I need to optimize this code, that basically checks if every character of string s1 is contained in s2 , taking in consideration doubles.

s1, s2 = list(s1), list(s2)
for s in s2:
    if s in s1:
        s1.remove(s)
    else:
        return False
return True

I did some research on map , iterators and generators, and I'm sure in one or more of these there is a solution, but right now I'm pretty confused and frustrated (I'm very new to python, just a couple weeks), so maybe you can help me understand what's the best strategy in this case. Thanks!

Answer 1

A solution using Counter that will handle duplicated characters correctly:

from collections import Counter
c1 = Counter(s1)
c2 = Counter(s2)
return all(c2[c]>=c1[c] for c in c1)

Answer 2

You can count the number of occurrences of each character in both strings. You also don't need to make either string a list: strings are their own iterators.

First, create a set as sets have an average lookup of O(1) . Then, iterate through the set and get the counts of each character. If any counts aren't equal, return False . It also scales much better as the size of the string grows, than your current solution:

s1 = 'Stack Overflow'
s2 = 'woltk fcrSeavO'

def equal_chars(s1, s2):
    chars = set(s2)
    for char in chars:
        if s1.count(char)!= s2.count(char):
            return False
    return True

print(equal_chars(s1, s2))

Answer 3

A slight adjustment on Adrien's great answer which is (maybe?) more efficient:

from collections import Counter

s1 = "hello"
s2 = "helo"

def count_chars(s1,s2):
    c2 = Counter(s2)
    for k,v in Counter(s1).items():
        if c2[k] < v:
            return False
    return True

print (count_chars(s1,s2))

result:

False