--- title: Python Filter Function published: true date: 2019-10-14 07:58:55 UTC tags: Python Tutorials,filter() in python,python,python filter functi canonical_url: https://pythongeeks.net/python-tutorials/python-filter-function/ --- Python `filter()` function constructs an iterator from elements of an iterable for which a function returns true. We can understand that `filter` will test every element of iterators to be true or not. **A Quick Example** ``` marks = [5, 7, 2, 8, 9] def is_pass_test(x): if m < 5: return False else: return True passes = filter(is_pass_test, marks) print(list(passes)) # Result: [7, 8, 9] ``` ![Python Filter Function, quickly filter your data in Python](https://i2.wp.com/pythongeeks.net/wp-content/uploads/2019/10/berlin_germany-wallpaper-1920x1080.jpg?resize=640%2C360&ssl=1)

Quickly filter your data in Python.
(Berlin – Source: Wallpapers Wide)

### Definition and Usage The Python `filter()` syntax is as follows: ``` filter(function, iterable) ``` - function: The function will be executed for each element of iterable. - iterable: The iterable to be filtered. ### Python Filter Examples #### **Example 1: Using lambda function with filter()** We can make above example a lot shorter by using `lambda` with `filter()` ``` marks = [5, 7, 2, 8, 9] passes = filter(lambda x: x > 5, marks) print(list(passes)) # Result: [7, 8, 9] ``` You don't know what is `lambda`, don't worry, read our article to understand it ([What's lambda syntax in Python](https://dev.to/thepythongeeks/python-lambda-function-3pfd-temp-slug-2323806)) #### **Example 2: Passing None function to filter()** ``` datas = [5, False, '', True, 'Filtered', None] passes = filter(None, datas) print(list(passes)) # Result: [5, True, 'Filtered'] ``` In this example, we passed None as a function parameter. However it is not a real None value, it means a default function. In this case, a default function equal to `lambda x: x` ### References As our goal to build a short and understandable tutorial. However, in case you would like to learn deeper, you should read below references: - From [Python Official Document](https://docs.python.org/3/library/functions.html#filter) - From [Python Tips Book](https://book.pythontips.com/en/latest/map_filter.html#filter) The post [Python Filter Function](https://pythongeeks.net/python-tutorials/python-filter-function/) appeared first on [Python Geeks](https://pythongeeks.net).

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Python Filter Function

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