The filter() method filters the given sequence with the help of a function that tests each element in the sequence to be true or not. Let's see a simple example of filter() function in python:
Example Usage of filter()
Python
# Function to check if a number is even
def even(n):
return n % 2 == 0
a = [1, 2, 3, 4, 5, 6]
b = filter(even, a)
# Convert filter object to a list
print(list(b))
Explanation:
- Function: even function checks if a number is divisible by 2.
- Filter: The filter() applies this function to each item in numbers.
- Result: A new iterable containing only even numbers is returned.
Let's explore filter() in detail:
Python filter() Syntax
The filter() method in Python has the following syntax:
Syntax: filter(function, sequence)
- function: A function that defines the condition to filter the elements. This function should return True for items you want to keep and False for those you want to exclude.
- iterable: The iterable you want to filter (e.g., list, tuple, set).
The result is a filter object, which can be converted into a list, tuple or another iterable type.
Let us see a few examples of the filter() function in Python.
Using filter() with lambda
For concise conditions, we can use a lambda function instead of defining a named function.
Python
a = [1, 2, 3, 4, 5, 6]
b = filter(lambda x: x % 2 == 0, a)
print(list(b))
Here, the lambda function replaces even and directly defines the condition x % 2 == 0 inline.
Combining filter() with Other Functions
We can combine filter() with other Python functions like map() or use it in a pipeline to process data efficiently.
Example: Filtering and Transforming Data
Python
a = [1, 2, 3, 4, 5, 6]
# First, filter even numbers
b = filter(lambda x: x % 2 == 0, a)
# Then, double the filtered numbers
c = map(lambda x: x * 2, b)
print(list(c))
Explanation:
- The filter() function extracts even numbers from numbers.
- The map() function doubles each filtered number.
- The combination simplifies complex data pipelines.
Filter() Function in Python
filter() in python
