Using modules and packages with the Python interactive interpreter

As well as calling modules and packages from a Python script, it is often useful to call them directly from the Python interactive interpreter. This is a great way of employing the rapid application development (RAD) technique for Python programming: you make a change of some sort to a Python module or package and immediately see the results of your change by calling that module or package from the Python interactive interpreter.

There are, however, a few limitations and issues to be aware of. Let's take a closer look at how you can use the interactive interpreter to speed up your development of modules and packages; we'll also see where a different approach might suit you better.

Start by creating a new Python module named stringutils.py, and enter the following code into this file:

import re

def extract_numbers(s):
    pattern = r'[+-]?\d+(?:\.\d+)?'
    numbers = []
    for match in re.finditer(pattern, s):
        number...