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filter() in python

  • Difficulty Level : Easy
  • Last Updated : 22 Apr, 2020

The filter() method filters the given sequence with the help of a function that tests each element in the sequence to be true or not.


filter(function, sequence)
function: function that tests if each element of a 
sequence true or not.
sequence: sequence which needs to be filtered, it can 
be sets, lists, tuples, or containers of any iterators.
returns an iterator that is already filtered.

# function that filters vowels
def fun(variable):
    letters = ['a', 'e', 'i', 'o', 'u']
    if (variable in letters):
        return True
        return False
# sequence
sequence = ['g', 'e', 'e', 'j', 'k', 's', 'p', 'r']
# using filter function
filtered = filter(fun, sequence)
print('The filtered letters are:')
for s in filtered:


The filtered letters are:

It is normally used with Lambda functions to separate list, tuple, or sets.

# a list contains both even and odd numbers. 
seq = [0, 1, 2, 3, 5, 8, 13]
# result contains odd numbers of the list
result = filter(lambda x: x % 2 != 0, seq)
# result contains even numbers of the list
result = filter(lambda x: x % 2 == 0, seq)


[1, 3, 5, 13]
[0, 2, 8]

Please refer Python Lambda functions for more details.

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