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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 returns 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}

Flowchart:

Flowchart: Count of elements in each group from list based groups of elements.

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Previous: Write a Python program to merge two or more lists into a list of lists, combining elements from each of the input lists based on their positions.
Next: Write a Python program to split values into two groups, based on the result of the given filtering function.

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Python: Tips of the Day

Floor Division:

When we speak of division we normally mean (/) float division operator, this will give a precise result in float format with decimals.

For a rounded integer result there is (//) floor division operator in Python. Floor division will only give integer results that are round numbers.

print(1000 // 300)
print(1000 / 300)

Output:

3
3.3333333333333335