Filter List Using Boolean Index Arrays

How can I use boolean inddex arrays to filter a list without using numpy? For example: >>> l = ['a','b','c'] >>> b = [True,False,False] >>> l[b] The res

Solution 1:

Python does not support boolean indexing but the itertools.compress function does exactly what you want. It return an iterator with means you need to use the list constructor to return a list.

>>>from itertools import compress>>>l = ['a', 'b', 'c']>>>b = [True, False, False]>>>list(compress(l, b))
['a']

Solution 2:

[a for a, t in zip(l, b) if t]
# => ["a"]

A bit more efficient, use iterator version:

from itertools import izip
[a for a, t in izip(l, b) if t]
# => ["a"]

EDIT: user3100115's version is nicer.

Solution 3:

Using enumerate

l = ['a','b','c']
b = [True,False,False]

res = [item for i, item inenumerate(l) if b[i]]

print(res)

gives

['a']