functions

A function is a unit or block of code that is callable. I can write statements that I can used to do something and call it at different time from when I write it. They can make code smaller and easier to read, test, reuse, maintain and improve.

Programming involves providing a process with input data and the process returning output data

argument -> program -> output_data

I think of it mathematically as mapping a function f with inputs x and an output of y

\[f(x) -> y\]

in other words

program(argument) -> output_data

program is the function that processes argument to return output_data

functions are defined using the def keyword, a name, parentheses and a colon at the end

The following tests cover different ways to make a function

• test_functions
• test_functions_w_positional_arguments
• test_functions_w_keyword_arguments
• test_functions_w_positional_and_keyword_arguments

---