How to Filter List Elements in Python?

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

Syntax:

filter(function, sequence)

Parameters:

• function : the function that tests if each element of a sequence true or not.
• sequence : the sequence which needs to be filtered. It can be any iterable object such as sets, lists, tuples, or containers.

Returns: The method returns an iterator that is already filtered.

Example – Filter a Python List with filter()

# function that filters vowels
from os import truncate

def even(x):
    if x%2==0:
        return True
    else:
        return False

# creating a list in Python
mylist= [3,5,1,5,7,8,2,6]

# using filter function to find even numbers
filtered = filter(even, mylist)

print('The even numbers are:')
for s in filtered:
    print(s)

Output

The even numbers are:
8
2
6

Example – Python Filter List with Lambda

Alternatively, we can use a lambda function statement to create the function to pass it as an argument to the*filter()* method.

# creating a list in Python
mylist= [3,5,1,5,7,8,2,6]

#filter all the odd numbers using list Comprehension
result = [x for x in mylist if x%2!=0]
print('The odd numbers are ',list(result))

#filter all the even numbers using list Comprehension
result = [x for x in mylist if x%2==0]
print('The even numbers are ',list(result))

Output

The odd numbers are [3, 5, 1, 5, 7]
The even numbers are [8, 2, 6]

Example – Filter with List Comprehension

The best way to filter the list elements is using the list comprehension statement [x for x in list if condition]. The condition can be replaced with any function which can be used as a filtering condition.

# creating a list in Python
mylist= [3,5,1,5,7,8,2,6]

#filter all the odd numbers using lambda
result = filter(lambda x: x % 2 != 0, mylist)
print('The odd numbers are ',list(result))

#filter all the even numbers using lambda
result = filter(lambda x: x % 2 == 0, mylist)
print('The even numbers are ',list(result))

Output

The odd numbers are [3, 5, 1, 5, 7]
The even numbers are [8, 2, 6]

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