Python: Count of elements in each group from list based groups of elements

Python List: Exercise - 216 with Solution

Write a Python program to group the elements of a list based on the given function and return the count of elements in each group.

• Use collections.defaultdict to initialize a dictionary.
• Use map() to map the values of the given list using the given function./li>
• Iterate over the map and increase the element count each time it occurs.

Sample Solution:

Python Code:

from collections import defaultdict
def count_by(lst, fn = lambda x: x):
  count = defaultdict(int)
  for val in map(fn, lst):
    count[val] += 1
  return dict(count)
from math import floor
print(count_by([6.1, 4.2, 6.3], floor)) 
print(count_by(['one', 'two', 'three'], len))

Sample Output:

{6: 2, 4: 1}
{3: 2, 5: 1}

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