In functional programming, the filter function is a higher-order function that takes a sequence (such as a list or tuple) and a function as arguments, and returns a new sequence containing only the elements of the original sequence for which the function returns True.
Here's an example of how to use the filter function in Python:
# Define a list of numbersnumbers = [1, 2, 3, 4, 5]# Define a function that tests if a number is evendef is_even(x): return x % 2 == 0# Use filter to select only the even numbers from the numbers listeven_numbers = filter(is_even, numbers)# Convert the filter object to a list and print the resultprint(list(even_numbers)) |
This will output [2, 4], which is the result of applying the is_even function to each element of the numbers list using the filter function.
The filter function is useful for selecting elements from a sequence that satisfy some condition. Like the map function, the filter function does not modify the original sequence, but instead returns a new sequence containing only the selected elements.
In Dask bags, the filter method can be used to select elements from a bag that satisfy some condition. This allows you to filter large datasets in parallel, which can be much faster than doing so sequentially.