Testing Automatically Using doctest

def collect_vowels(s):
    """ (str) -> str
    Return the vowels (a, e, i, o, and u) from s.
    >>> collect_vowels('Happy Anniversary!')
    'aAiea'
    >>> collect_vowels('xyz')
    ''
    """
    vowels = ''
    for char in s:
        if char in 'aeiouAEIOU':
            vowels = vowels + char
    return vowels

Using doctest

After running the module containing collect_vowels, in the Python shell, import the doctest module, then call doctest.testmod():

>>> import doctest
>>> doctest.testmod()
TestResults(failed=0, attempted=2)

More Examples

Consider this code:

def get_divisors(num, possible_divisors):
    """ (int, list of int) -> list of int
    
    Return a list of the values from possible_divisors
    that are divisors of num.
    
    >>> get_divisors(8, [1, 2, 3])
    [1, 2]
    >>> get_divisors(4, [-2, 0, 2])
    [2]
    """

    divisors = []

    for item in possible_divisors:
        if item != 0 and num % item == 0:
            divisors.append(item)

    return divisors
    
if __name__ == __main__:
    import doctest
    doctest.testmod()

Creating Your Own Types

class MyString(str):
        def check(self):
                """ (MyString) -> bool
                >>> s = MyString("abc")
                >>> s.check()
                False
                >>> d = MyString("aba")
                >>> d.check()
                True
                """
                return self[0] == self[-1]

if __name__ == "__main__":
    import doctest
    doctest.testmod()

Testing Automatically Using unittest

import unittest
import divisors

class TestDivisors(unittest.TestCase):
    """Example unittest test methods for get_divisors."""
        
    def test_divisors_example_1(self):
        """Test get_divisors with 8 and [1, 2, 3]."""
                
        actual = divisors.get_divisors(8, [1, 2, 3])
        expected = [1, 2]
        self.assertEqual(expected, actual)      
                
    def test_divisors_example_2(self):  
        """Test get_divisors with 4 and [-2, 0, 2]."""
                
        actual = divisors.get_divisors(4, [-2, 0, 2])
        expected = [-2, 2]
        self.assertEqual(expected, actual)      

Python Image Library

Example 1.

import Image, ImageDraw
import math
im = Image.new( 'RGB', (400,400), "white") # create a new black image

draw = ImageDraw.Draw(im)


draw.line((0, 0) + (400, 400), fill="grey", width = 1)
draw.ellipse((20-5, 10-5, 20+5, 10+5), fill="green")
draw.text((100, 200), "Text", "black")

im.show()       

Example 2.

import Image, ImageDraw

im = Image.new( 'RGB', (400, 400), "white") # create a new black image

draw = ImageDraw.Draw(im)

point1 = raw_input().split()
point2 = raw_input().split()
x1, y1 = int(point1[0]), int(point1[1])
x2, y2 = int(point2[0]), int(point2[1])
xm = (x1 + x2) / 2
ym = (y1 + y2) / 2

draw.line((x1, y1) + (x2, y2), fill = "black", width = 3)
draw.ellipse((xm - 5, ym - 5, xm + 5, ym + 5), fill = "green")

im.show()