Python, Named arguments: Pure Genius

2007-12-21T00:00:00-08:00

I decided I want to learn python, if only to learn Django and to "get" what all the python hub-bub is about.

Python's named arguments in function calls is pure genius. Let me explain.

In PHP, and many other languages you can define a function as such:

function foo($a = 2, $b = 2)
{
    return pow($a,$b);
}

If you follow, foo() will give you 4. foo(3) is 9 and foo(99,0) is 1. In python we can do the same thing, but it'll pay to use some better variable names:

def foo(base=2, exponent=2):
    return base**exponent

Similarly foo() will give you 4. foo(3) is 9 and foo(99,0) is 1. But what if we forgot what the order was? Did base come first or was it exponent? We can do this:

foo(exponent=99, base=2)

Since base and exponent both have default values, we can even omit base and let it use the default:

foo(exponent=10)

This means rather than passing an $options array to my functions and checking whether an option was set or not, I can just specify which options I want in my function call. Or instead of remembering the order of the arguments, I can use whatever order suits me. Or instead of calling a function like bar(null, null, null, 2) I can just skip those first three arguments all together.

A side effect of this, is now there's a real use, even for simple functions, to give your variables easy to remember names.

Dave Dash

Python, Named arguments: Pure Genius