In this article, we will see about python map and filter inbuilt methods. In every functional programming you will come across these and is very important to know their usages.
Map applies a function on every element in the iterable and yields the results.
Syntax of map is as follows
Let’s check out a small example. We will get the nth root of every element in the given list of elements.
def raise_to(p): def inner(x): return pow(x, p) return inner cube = raise_to(3) print(list(map(cube, [2, 3, 4, 5]))) OUTPUT [8, 27, 64, 125]
In the above program we applied function cube to every element using map in the iterable. The output returns raises every element to the power of 3. The function applies on the iterable till it is exhausted.
Filter is used to remove elements from the iterable for which the function returns False.
Syntax of filter is as follows
Let us see one common example for filter where I want to filter only even numbers from the given list.
def is_even(x): return x if x % 2 == 0 else 0 list(filter(is_even, range(10))) OUTPUT [2, 4, 6, 8]