in this post, we’ll see how to use reduce() function in python to process a list. This function is used to apply a function to all of the list elements that is supplied as an argument. This function is defined under “functools” module.
Reduce() comes in helpful when you need to apply a function to an iterable and reduce it to a single cumulative value.
According to the documentation for reduce(), the function has the following signature:
reduce(func, iterable[, initial])
The reduce function takes three arguments::
func: This is the cumulative function that each element in the iterable is applied to.
iterable: Any python iterable data structure
initial: this is the optional value and acts as a default when the iterable is empty.
Python reduce() with inbuilt function
Let’s take an example that’ll return the sum of the list number. We’ll use the operator inbuild add() method that will return the sum up the all numbers.
import operator import functools sequence = [2,8,9,10,16] sum = functools.reduce( operator.add, sequence,0) print(sum)
Output:
45
in the above code, We are passing operator.add() function and sequence as arguments, You get an output that shows all the operations that reduce() performs to come up with a final result of 45. The operations are equivalent to ((((2 + 8) + 9) + 10) + 16) = 45.
Python reduce() with Custom function
Let’s take a user-defined function(custom method) as an argument with reduce() function.
import functools def my_add(a, b): result = a + b return result sequence = [2,8,9,10,17] sum = functools.reduce( my_add, sequence,0) print(sum)
Output:
46
Python reduce() method with initial value
Let’s pass some initial value to the reduce function, I am passing 10 as the initial value to the above code.
import functools def my_add(a, b): result = a + b return result sequence = [2,8,9,10,17] sum = functools.reduce( my_add, sequence,10) print(sum)
Output:
56
As you can see output, the 10 value has been added to the sum of the iterable.