Python Function Rules: Definition Guide

The rules for defining functions in Python are as follows:

1. Define a function using the keyword def, followed by the function’s name and parentheses. The parentheses can contain parameters separated by commas.
2. Function names should begin with a letter or underscore, and can contain letters, numbers, and underscores.
3. The parameters of a function are optional and default values can be specified when defining the function.
4. The function body must be indented, usually with four spaces or a tab.
5. A function can return a value by using the keyword “return” followed by the value to be returned.
6. A function may not have a return value, in which case it returns None if the return statement is not used.
7. A function can take any number of parameters, including a variable number of parameters. Variable number of parameters are indicated by an asterisk (*).
8. The function can accept keyword arguments, which are represented by double asterisks (**) in Python.
9. Functions can use both positional and keyword arguments when called.
10. Functions can be nested, meaning that another function can be defined within the body of a function.
11. A function can be assigned to a variable, passed as an argument to another function, or returned as a value.
12. Function names should be descriptive to improve code readability and maintainability.