Partial Functions

A partial function is a regular function with some of its arguments already filled in. You hand it a few arguments now, and the result is a new callable that only needs the rest. Python ships this idea as functools.partial, and it shows up in callbacks with bound state, simplified signatures for repeat calls, and configured versions of general helpers. This chapter covers how partial works, when to use it instead of a lambda, how it composes with map and filter, the related partialmethod for class methods, and a few practical caveats.