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Comprehensions & generators

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

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Comprehensions & generators easy

How to Lazily Transform Items in Python with a Generator

Map a transform function over an iterable lazily with a generator so items are processed on demand, not up front.

generators lazy evaluation mapping
Python 
def lazy_map(items, transform):
    for item in items:
        yield transform(item)

def double(x):
    return x * 2

def upper(s):
    return s.upper()

if __name__ == "__main__":
    numbers = [1, 2, 3, 4, 5]
    doubled = lazy_map(numbers, double)
    print("Doubled numbers:", end=" ")
    for value in doubled:
  …
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