PYTHON

python collections counter

import collections

arr = ['a', 'a', 'b', 'b', 'b', 'c']

# set the elements frequencies using Counter class
elements_count = collections.Counter(arr)

# printing the element and the frequency
for key, value in elements_count.items():
    print(f"{key}: {value}")

# output
# a: 2
# b: 3
# c: 1

collections counter

# importing the collections module
import collections
# intializing the arr
arr = [1, 1, 1, 2, 2, 2, 2, 3, 3, 3, 3, 3]
# getting the elements frequencies using Counter class
elements_count = collections.Counter(arr)
# printing the element and the frequency
for key, value in elements_count.items():
   print(f"{key}: {value}")

python collections counter methods

c.total()                       # total of all counts
c.clear()                       # reset all counts
list(c)                         # list unique elements
set(c)                          # convert to a set
dict(c)                         # convert to a regular dictionary
c.items()                       # convert to a list of (elem, cnt) pairs
Counter(dict(list_of_pairs))    # convert from a list of (elem, cnt) pairs
c.most_common()[:-n-1:-1]       # n least common elements
+c                              # remove zero and negative counts