Nrthugu

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}