Partials

We already know that we can apply unary functions to multiple elements using map, and apply binary functions using reduce.

There is a whole set of functions that accepts a callable in Python and applies it to a set of items.

The major problem is that frequently the callable we want to apply might have a slightly different signature, and while we can solve the issue by wrapping the callable into another callable that adapts the signature, this is not very convenient if you just want to apply a function to a set of items.

For example, if you want to multiply all numbers in a list by 3, there is no function that multiplies a given argument by 3.

How to do it...

We can easily adapt operator.mul to be a unary function and then pass it to map to apply it to the whole list:

>>> import functools, operator
>>>
>>> values = range(10)
>>> mul3 = functools.partial(operator.mul, 3)
>>> list(map(mul3, values))
[0, 3, 6, 9, 12, 15, 18, 21, 24, 27]

As you can...