Tutorial by Examples

To filter discards elements of a sequence based on some criteria: names = ['Fred', 'Wilma', 'Barney'] def long_name(name): return len(name) > 5 Python 2.x2.0 filter(long_name, names) # Out: ['Barney'] [name for name in names if len(name) > 5] # equivalent list comprehension #...

If the function parameter is None, then the identity function will be used: list(filter(None, [1, 0, 2, [], '', 'a'])) # discards 0, [] and '' # Out: [1, 2, 'a'] Python 2.x2.0.1 [i for i in [1, 0, 2, [], '', 'a'] if i] # equivalent list comprehension Python 3.x3.0.0 (i for i in [1, 0...

filter (python 3.x) and ifilter (python 2.x) return a generator so they can be very handy when creating a short-circuit test like or or and: Python 2.x2.0.1 # not recommended in real use but keeps the example short: from itertools import ifilter as filter Python 2.x2.6.1 from future_built...

There is a complementary function for filter in the itertools-module: Python 2.x2.0.1 # not recommended in real use but keeps the example valid for python 2.x and python 3.x from itertools import ifilterfalse as filterfalse Python 3.x3.0.0 from itertools import filterfalse which works...