filter() in python
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.
syntax:
filter(function, sequence) Parameters: 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: 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 else: 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: print(s) |
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Output:
The filtered letters are: e e
Application:
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) print(list(result)) # result contains even numbers of the list result = filter(lambda x: x % 2 == 0, seq) print(list(result)) |
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Output:
[1, 3, 5, 13] [0, 2, 8]
Please refer Python Lambda functions for more details.
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