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Comprehensions & generators

List/dict/set comprehensions, generator expressions, and lazy iteration.

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Comprehensions & generators easy

How to Group Data in Python with defaultdict and Comprehensions

Group a list of items by a computed key using a defaultdict-based generator helper and an alternative dictionary comprehension approach.

grouping defaultdict comprehensions
Python 
from collections import defaultdict

def group_by(data, key_func):
    """Group items in data by the value returned by key_func."""
    result = defaultdict(list)
    for item in data:
        result[key_func(item)].append(item)
    return dict(result)

def group_by_comprehension(data, key_func):
    """Same grouping …
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