A user-defined function is a named sequence of statements that perform a computation.
Functions provide benefits as they
Functions are defined once with the def statement. Then, they may be called many times with the call operator ().
They may process parameterized inputs, passed in as arguments, and output a return value.
Arguments may be passed in by position or keyword. Some functions may even require keyword-only arguments.
Lambda expressions create anonymous functions.
Functions are a special kind of callables. Any object that may be called with the call operator () is a callable. Built-in functions and constructors are other kinds of callables.
Core Python can be extended with code from either the standard library or third-party libraries.
Outside Jupyter notebooks, Python code is put into modules that are grouped in packages.