Python: Grouping a sequence of key-value pairs into a dictionary of lists

Python dictionary: Exercise-46 with Solution

Write a Python program to create a dictionary grouping a sequence of key-value pairs into a dictionary of lists.

Sample Solution:

Python Code:

def grouping_dictionary(l):
    result = {}
    for k, v in l:
         result.setdefault(k, []).append(v)
    return result
colors = [('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]
print("Original list:")
print(colors)
print("\nGrouping a sequence of key-value pairs into a dictionary of lists:")
print(grouping_dictionary(colors))

Sample Output:

Original list:
[('yellow', 1), ('blue', 2), ('yellow', 3), ('blue', 4), ('red', 1)]

Grouping a sequence of key-value pairs into a dictionary of lists:
{'yellow': [1, 3], 'blue': [2, 4], 'red': [1]}

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