Partial Functions in Python?

Everybody loves to write reusable code, right? Then partial function is a cool thing to learn. Partial functions allows us to derive a function with x parameters to a function with fewer parameters and constant values set for the more limited function.

We can write partial functional application in python through functools library. Below is a simple example of partial function from the functools library with the add function from the operator library.

>>> from functools import *
>>> from operator import *
>>> add(1,2)
3
>>> add1 = partial(add, 4)
>>> add1(6)
10
>>> add1(10)
14

Partial is a higher order function which takes a function as input (like map and filter) but it also returns a function that can be used in the same way as any other function in your program.

>>> list(map (add1, [1, 2, 3, 4, 5]))
[5, 6, 7, 8, 9]
>>> seven = partial(add1, 3)
>>> seven()
7

We can also use partial on object methods, for e.g. to generate a list of default strings −

>>> str1 = "Hello, Python"
>>> helloStr = partial(str1.replace, "Python")
>>> helloStr("Tutorialspoint")
'Hello, Tutorialspoint'
>>> helloStr("Java")
'Hello, Java'

Partial function application is a very useful tools especially where you need to apply a range of different input to a single object or need to bind one of the arguments to a function to be constant.

Python function helps you to write your code easily and easier to maintain.