Python filter() Function
Python Built-in FunctionsDescription
filter()The function is used to filter sequences, filtering out elements that do not meet the conditions, and returning a new list composed of elements that meet the conditions.
It accepts two parameters: the first is a function, and the second is a sequence. Each element of the sequence is passed as a parameter to the function for evaluation, which then returns True or False. Finally, the elements that return True are placed in a new list.
Note:Python 2.7 returns a list, while Python 3.x returns an iterator object. For details, see:Python 3 filter() Function
Syntax
The following is the syntax for the filter() method:
filter(function, iterable)
Parameters
- function -- The judgment function.
- iterable -- The iterable object.
Return Value
Returns a list.
Examples
The following shows examples of using the filter function:
Filter out all odd numbers in the list:
#!/usr/bin/python
# -*- coding: UTF-8 -*-
def is_odd(n):
return n % 2 == 1
newlist = filter(is_odd, [1, 2, 3, 4, 5, 6, 7, 8, 9, 10])
print(newlist)
Output result:
[1, 3, 5, 7, 9]
Filter out numbers from 1 to 100 whose square root is an integer:
#!/usr/bin/python
# -*- coding: UTF-8 -*-
import math
def is_sqr(x):
return math.sqrt(x) % 1 == 0
newlist = filter(is_sqr, range(1, 101))
print(newlist)
Output result:
[1, 4, 9, 16, 25, 36, 49, 64, 81, 100]Other Extensions