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Python3 filter() Function

Python3 Built-in Functions


Description

The filter() function is used to filter a sequence, removing elements that do not meet the specified condition. It returns an iterator object. If you want to convert it to a list, you can use list() for the conversion.

This function takes two arguments: the first is a function, and the second is a sequence. Each element of the sequence is passed as an argument to the function for evaluation, returning either True or False. Finally, elements that return True are placed into a new list.

Syntax

Here is the syntax for the filter() method:

filter(function, iterable)

Parameters

Return Value

Returns an iterator object.


Examples

Below are examples of using the filter function:

Filter out all odd numbers from a list:

#!/usr/bin/python3

def is_odd(n):
    return n % 2 == 1

tmplist = filter(is_odd, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
newlist = list(tmplist)
print(newlist)

Output:

[1, 3, 5, 7, 9]

Filter out numbers from 1 to 100 whose square roots are integers:

#!/usr/bin/python3

import math
def is_sqr(x):
    return math.sqrt(x) % 1 == 0

tmplist = filter(is_sqr, range(1, 101))
newlist = list(tmplist)
print(newlist)

Output:

[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]

Python3 Built-in Functions

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