PEP 202 – List Comprehensions | peps.python.org
Following system colour scheme
Selected dark colour scheme
Selected light colour scheme
This PEP describes a proposed syntactical extension to Python, list
comprehensions.
It is proposed to allow conditional construction of list literals using for and
if clauses. They would nest in the same way for loops and if statements nest
now.
List comprehensions provide a more concise way to create lists in situations
where map() and filter() and/or nested loops would currently be used.
>>> print [i for i in range(10)]
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9]
>>> print [i for i in range(20) if i%2 == 0]
[0, 2, 4, 6, 8, 10, 12, 14, 16, 18]
>>> nums = [1, 2, 3, 4]
>>> fruit = ["Apples", "Peaches", "Pears", "Bananas"]
>>> print [(i, f) for i in nums for f in fruit]
[(1, 'Apples'), (1, 'Peaches'), (1, 'Pears'), (1, 'Bananas'),
(2, 'Apples'), (2, 'Peaches'), (2, 'Pears'), (2, 'Bananas'),
(3, 'Apples'), (3, 'Peaches'), (3, 'Pears'), (3, 'Bananas'),
(4, 'Apples'), (4, 'Peaches'), (4, 'Pears'), (4, 'Bananas')]
>>> print [(i, f) for i in nums for f in fruit if f[0] == "P"]
[(1, 'Peaches'), (1, 'Pears'),
(2, 'Peaches'), (2, 'Pears'),
(3, 'Peaches'), (3, 'Pears'),
(4, 'Peaches'), (4, 'Pears')]
>>> print [(i, f) for i in nums for f in fruit if f[0] == "P" if i%2 == 1]
[(1, 'Peaches'), (1, 'Pears'), (3, 'Peaches'), (3, 'Pears')]
>>> print [i for i in zip(nums, fruit) if i[0]%2==0]
[(2, 'Peaches'), (4, 'Bananas')]
List comprehensions become part of the Python language with release 2.0,
documented in .