Doctests and test driven development

Automated testing with doctest

doctest is a module in the Python standard library which makes innovative use of Python's docstring, interactive shell, and introspection capabilities.

docstrings

Python's docstrings provide an easy way to document modules, classes, methods, and functions. A docstring is simply a string constant that occurs as the first statement of an object's definition. Here is an example from the chapter on trees illustrating its use:

def total(tree):
    """total(tree) -> sum

      Return the sum of the values of the elements of a tree of numbers.
    """
    if tree == None: return 0
    return total(tree.left) + total(tree.right)

Assuming the example above is in a module named trees.py, the following is now possible:

>>> from trees import *
>>> print total.__doc__
total(tree) -> sum

      Return the sum of the values of the elements of a tree of numbers.