# What is filter() in python?

PythonServer Side ProgrammingProgramming

Through the filter method, we filter out specific elements of a list using a filter condition defined in a separate function. So we first create a user-defined function which will mention the criteria of filtering. Together this function and the supplied list will be taken as parameters to the filter function to give us the result.

## Syntax

filter(filter_function, sequence)

## Example

In the below example we create a function that will find the even numbers present in a list. Then it will discard them (return false). The remaining odd numbers will be added to the final list. We can modify this function to filter out numbers divisible by 3 or 5 or so.

Live Demo

num_list = [6,17, 32, 11, 21, 132]
def remove_even(x):
if x%2 ==0 :
return False
else:
return True
odd_nos = filter(remove_even, num_list)
for x in odd_nos:
print(x)


## Output

Running the above code gives us the following result −

17
11
21

## Example

We can use the same approach to filter out vowels from a given list of alphabets. Here

Live Demo

letters = ['t','u','t','o','r','i','a','l','s']
def get_vowels(c):
if c in ['a','e','i','o','o']:
return True
else:
return False
vowel_list = filter(get_vowels, letters)
for w in vowel_list:
print(w)

## Output

Running the above code gives us the following result −

u
o
i
a
Updated on 17-Oct-2019 12:48:32