Test-driven development1 (TDD) is a technique that is used by software developers. The technique is to first write down a few examples that show how the code should work, before the actual program code is written to resolve the problem in question. Kent Beck that developed the technique in 2003, says the following about it: " "TDD encourages simple designs and inspires confidence".
The Python Standard Library contains a module doctest2 with which the TDD principle can be easily applied when writing Python program code. Indeed, this module includes a function testmod which looks for pieces of text in the docstrings of the program code that look like interactive Python sessions. These snippets are then actually carried out, to determine whether they indeed work as indicated. To submit your program code to a doctest it is therefore sufficient to include representative examples in the docstrings of your functions and adding the following snippet at the end of your Python modules:
if __name__ == '__main__':
import doctest
doctest.testmod()We want to write a Python module in which we bring together a number of functions that can be used to analyze words and sentences. The following code fragment already contains the first step in this direction. We have already worked out the header of the functions that determines the name and parameters. For the parameter s a string should always be passed, and for the parameter l a list of strings must always be passed. Through a few examples in the form of interactive Python sessions we have already indicated in the docstring of the functions how the functions should work .
Based on the examples, it is now your job to derive what result the function should return for arbitrary values of the appropriate data type that are passed as an argument to the function. It is envisaged that the function does not only work correctly for the given examples, but also for other values of the arguments. Implement the necessary Python instructions in the body of each of the functions, so the functions pass the doctest. Also add a brief description of the procedure to the docstring of each function.
def onlyletters(s):
"""
>>> onlyletters('what?')
'what'
>>> onlyletters('"now!"')
'now'
>>> onlyletters('?+="word!,@$()"')
'word'
"""
def doublehyphen(s):
"""
>>> doublehyphen('well--being')
True
>>> doublehyphen('more')
False
>>> doublehyphen('creature')
False
>>> doublehyphen('merry-go--round')
True
>>> doublehyphen('yo---yo')
False
"""
def wordlist(s):
"""
>>> wordlist('I wish to wish the wish you wish to wish, but if you wish the wish the witch wishes, I won't wish the wish you wish to wish.')
['what', 'was', 'was', 'before', 'was', 'was', 'was']
>>> wordlist('Peter Piper picked a peck of pickled peppers as a pick-me-up.')
['Peter', 'Piper', 'picked', 'a', 'peck', 'of', 'pickled', 'peppers', 'as', 'pickmeup']
>>> wordlist('I sell unsifted--thistles to thistle-sifters.')
['I', 'sell', 'unsifted', 'thistles', 'to', 'thistlesifters']
"""
def numberofwords(s, l):
"""
>>> numberofwords('to', ['i', 'wish', 'to', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish', 'but', 'if', 'you', 'wish', 'the', 'wish', 'the', 'witch', 'wishes', 'i', 'will', 'not', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish'])
['to', 3]
>>> numberofwords('wish', ['i', 'wish', 'to', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish', 'but', 'if', 'you', 'wish', 'the', 'wish', 'the', 'witch', 'wishes', 'i', 'will', 'not', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish'])
['wish', 11]
>>> numberofwords('i', ['i', 'wish', 'to', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish', 'but', 'if', 'you', 'wish', 'the', 'wish', 'the', 'witch', 'wishes', 'i', 'will', 'not', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish'])
['i', 2]
>>> numberofwords('is', ['i', 'wish', 'to', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish', 'but', 'if', 'you', 'wish', 'the', 'wish', 'the', 'witch', 'wishes', 'i', 'will', 'not', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish'])
['is', 0]
"""
def uniquewords(l):
"""
>>> uniquewords(['I', 'wish', 'to', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish', 'but', 'if', 'you', 'wish', 'the', 'wish', 'the', 'witch', 'wishes', 'I', 'will', 'not', 'wish', 'the', 'wish', 'you', 'wish', 'to', 'wish'])
['but', 'i', 'if', 'not', 'the', 'to', 'will', 'wish', 'wishes', 'witch', 'you']
>>> uniquewords(['If', 'Stu', 'chews', 'shoes', 'should', 'Stu', 'choose', 'the', 'shoes', 'he', 'chews'])
['chews', 'choose', 'he', 'if', 'shoes', 'should', 'stu', 'the']
"""
def longestword(l):
"""
>>> longestword(['apple', 'pear', 'mango'])
5
>>> longestword(['I', 'am', 'the', 'coolest'])
7
>>> longestword(['foo', 'supercalifragilisticexpialidocious', 'bar'])
34
"""
if __name__ == '__main__':
import doctest
doctest.testmod()