Partial Function Application -- Advantages over normal function?

Steven D'Aprano steve+comp.lang.python at
Mon Jul 18 17:08:22 CEST 2011

Kurian Thayil wrote:

> Hi,
> I am a newbie in python and would like to learn GUI programming. I would
> like to know what exactly is Partial Function Applicaton
> (functool.partial())? Or how is it advantageous compared to normal
> functions? Or is there any advantange? Thanks in advance.

It is mostly for functional programming style.

But one lucky side-effect of the implementation is that partial functions
*may* sometimes be faster than the alternative written in pure Python,
provided the original function is written in C:

from functools import partial
from operator import add

def add_one(x):
    return add(1, x)  # Like 1+x

add_two = partial(add, 2)

from timeit import Timer
setup = "from __main__ import add_one, add_two"
t1 = Timer("add_one(42)", setup)
t2 = Timer("add_two(42)", setup)

And in action:

>>> t1.timeit()
>>> t2.timeit()

So in this example, the partial function is about twice as fast as the one
written in Python.

This does not necessarily apply for all functions, but it sometimes is


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