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Python List Comprehensions

Yos Riady
August 06, 2013

Python List Comprehensions

A lightning talk on Python list comprehensions for Grow Beyond with Google.

Yos Riady

August 06, 2013
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  1. Python List
    Comprehensions

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  2. ‘Traditional’ way
    Constructing a list of squares of even numbers:
    squares_of_evens = []
    # range(10) -> [0,1,2,3,4,5,6,7,8,9]
    for n in range(10):
    if n%2==0:
    squares_of_evens.append(n*n)
    print squares_of_evens #[0, 4, 16, 36, 64]
    It works - but ugly and slow!

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  3. Construct lists in a concise way
    General syntax:
    new_list = [new_item for item in input_list]
    new_list = [new_item for item in input_list if some_condition]
    Squares of even numbers:
    squares_of_evens = [n*n for n in range(10) if (n%2 == 0)]
    print squares_of_evens #[0, 4, 16, 36, 64]

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  4. Thanks!

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