Luke Lee

Software Engineer

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Partial Function Application in Python

Spend a few minutes and read this great article on partial function application in Python.

I've used partial quite a bit in the past when dealing with map as the author discusses. In addition, I've used partial in situations where it leads to more readable function calls, especially with calls that have lots of optional arguments. Here's a good example from my own usage of matplotlib and the subtitle method:

It's much more readable to call set_title all over a module than the cumbersome and error-prone suptitle method with its' myriad of optional arguments. You can also decrease duplicated code and lock-down arguments by using partial functions in this way.

Finally, here's something about partial functions that Christian Schramm taught me in his excellent article:

So there we have one very practical advantage of using the partial function [from] functools over our own wrapper: We avoid constructing (and destructing) another stack frame, which is a costly thing to do if done very often (read: It's slow). Now we all know about how “premature optimization is the root of all evil”, but using the partial function is typically not much an effort, really. If the partial version is no more complicated than a wrapper, we might as well use it.

Published: 12-04-2013 14:34:17