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Python's filter() Function

Last Updated on Wednesday 5th Oct 2022

filter in python

The filter() is a built-in function that allows you to process an iterable (list, tuple etc.) for which a function returns True.

Syntax

			
					filter(function, iterable)

			
	

Note: Since filter() is a built-in function, you don’t have to import anything to be able to use it in your code.

Arguments

  • function - The first argument to filter() is a function object, which means that you need to pass a function without calling it with a pair of parentheses.
  • iterable - The second argument, iterable, can hold any Python iterable, such as a list, tuple, or set.

Return Value

Note: You can easily convert iterators to sequences like lists, tuples, strings etc.

filter python

Example 1

Filter out the number less than 20 in given list.

			
					numberList = [11, 22, 33, 14, 15, 16, 20, 4, 5, 1, 43, 55, 66]

def getLessThan20Func(numList):
    if(numList < 20):
        return True
    else:
        return False

numbers = filter(getLessThan20Func, numberList)

for i in numbers:
    print(i)

			
	

Output

			
					11
14
15
16
4
5
1

			
	

Example 2

Lets filter the vowels in given list

			
					letters = ['a', 'b', 'c', 'd', 'e', 'f', 'g', 'h', 'i', 'j', 'k', 'l', 'm', 'n',  'o']

def filterVowels(letter):
    vowels = ['a', 'e', 'i', 'o', 'u']
    return True if letter in vowels else False

filtered = filter(filterVowels, letters)

vowels = tuple(filtered)
print(vowels)

			
	

Output

			
					('a', 'e', 'i', 'o')

			
	

Example 3

Let’s filter the even numbers from the given list of numbers using the filter function

			
					numberList = [11, 22, 33, 14, 15, 16, 20, 4, 5, 1, 43, 55, 66]

def isEven(numList):
    if(numList %2 == 0):
        return True
    else:
        return False

numbers = filter(isEven, numberList)

for i in numbers:
    print(i)

			
	

Output

			
					22
14
16
20
4
66

			
	
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