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Python: Groups the elements of a given list based on the given function

Python dictionary: Exercise-69 with Solution

Write a Python program to group the elements of a given list based on the given function.

  • Use collections.defaultdict to initialize a dictionary.
  • Use fn in combination with a for loop and dict.append() to populate the dictionary.
  • Use dict() to convert it to a regular dictionary.

Sample Solution:

Python Code:

from collections import defaultdict
from math import floor
def test(lst, fn):
  d = defaultdict(list)
  for el in lst:
    d[fn(el)].append(el)
  return dict(d)
nums = [7,23, 3.2, 3.3, 8.4]
print("Original list & function:")
print(nums," Function name: floor:")
print("Group the elements of the said list based on the given function:")
print(test(nums, floor))
print("\n")
print("Original list & function:")
colors = ['Red', 'Green', 'Black', 'White', 'Pink']
print(colors," Function name: len:")
print("Group the elements of the said list based on the given function:")
print(test(colors, len))

Sample Output:

Original list & function:
[7, 23, 3.2, 3.3, 8.4]  Function name: floor:
Group the elements of the said list based on the given function:
{7: [7], 23: [23], 3: [3.2, 3.3], 8: [8.4]}


Original list & function:
['Red', 'Green', 'Black', 'White', 'Pink']  Function name: len:
Group the elements of the said list based on the given function:
{3: ['Red'], 5: ['Green', 'Black', 'White'], 4: ['Pink']}

Flowchart:

Flowchart: Groups the elements of a given list based on the given function.

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Previous: Write a Python program to combines two or more dictionaries, creating a list of values for each key.
Next: Write a Python program to map the values of a given list to a dictionary using a function, where the key-value pairs consist of the original value as the key and the result of the function as the value.

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Python: Tips of the Day

Decapitalizes the first letter of a string:

Example:

def tips_decapitalize(s, upper_rest=False):
  return s[:1].lower() + (s[1:].upper() if upper_rest else s[1:])
print(tips_decapitalize('PythonTips'))
print(tips_decapitalize('PythonTips', True)) 

Output:

pythonTips
pYTHONTIPS