Creating a partial function

When we look at functions such as reduce(), sorted(), min(), and max(), we see that we'll often have some permanent argument values. For example, we might find a need to write something like this in several places:

    reduce(operator.mul, ..., 1) 

Of the three parameters to reduce(), only one - the iterable to process - actually changes. The operator and the base value arguments are essentially fixed at operator.mul and 1.

Clearly, we can define a whole new function for this:

    def prod(iterable): 
        return reduce(operator.mul, iterable, 1) 

However, Python has a few ways to simplify this pattern so that we don't have to repeat the boilerplate def and return statements.

How can we define a function that has some parameters provided in advance?

Note that the goal here is different from providing default values. A partial function doesn't provide a way to override the defaults. Instead, we want to create as many partial functions as we need, each...