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I am experimenting with Python standard library Collections.

I have a Counter of things as

>>> c = Counter('achdnsdsdsdsdklaffaefhaew')
>>> c
Counter('a': 4,
 'c': 1,
 'h': 2,
 'd': 5,
 'n': 1,
 's': 4,
 'k': 1,
 'l': 1,
 'f': 3,
 'e': 2,
 'w': 1)

What I want now is to somehow get subset of this counter as another Counter object. Just like this:

>>> new_c = do_subset(c, [d,s,l,e,w])
>>> new_c
Counter('d': 5,
 's': 4,
 'l': 1,
 'e': 2,
 'w': 1)

Thank you in advance.

You could simply build a dictionary and pass it to Counter:

from collections import Counter

c = Counter('a': 4,
 'c': 1,
 'h': 2,
 'd': 5,
 'n': 1,
 's': 4,
 'k': 1,
 'l': 1,
 'f': 3,
 'e': 2,
 'w': 1)


def do_subset(counter, lst):
 return Counter(k: counter.get(k, 0) for k in lst)


result = do_subset(c, ['d', 's', 'l', 'e', 'w'])

print(result)

Output

Counter('d': 5, 's': 4, 'e': 2, 'l': 1, 'w': 1)

You can access each key in c and assign its value to the same key in a new dict.

import collections
c = collections.Counter('achdnsdsdsdsdklaffaefhaew')

def subsetter(c, sub):
 out = 
 for x in sub:
 out[x] = c[x]
 return collections.Counter(out)

subsetter(c, ["d","s","l","e","w"])

Yields:

'd': 5, 'e': 2, 'l': 1, 's': 4, 'w': 1