** Write a program madlib4.py that modifies the getKeys method of madlib2.py to use a while loop. (This is not an animation program, but this section is where you have had the most experience with while loops!)

Hints: This is actually the most natural approach. I avoided while loops initially, when only for loops had been discussed. It is redundant in the original approach, however, to find every instance of '{' to count the number of repetitions and then find them all again when extracting the cue keys. A more natural way to control the loop is a while loop stopping when there are no further occurrences of '{' to find. This involves some further adjustments. You must cut the loop in a different place (to end after searching for '{'). As discussed before, cutting a loop in a different place may require changes before and after the loop, too.

madlib2.py:

""" madlib2.py Interactive display of a mad lib, which is provided as a Python format string, with all the cues being dictionary formats, in the form {cue}.

In this version, the cues are extracted from the story automatically, and the user is prompted for the replacements.

Original verison adapted from code of Kirby Urner """

def getKeys(formatString): '''formatString is a format string with embedded dictionary keys. Return a set containing all the keys from the format string.'''

keyList = list() end = 0 repetitions = formatString.count('{') for i in range(repetitions): start = formatString.find('{', end) + 1 # pass the '{' end = formatString.find('}', start) key = formatString[start : end] keyList.append(key) # may add duplicates

return set(keyList) # removes duplicates: no duplicates in a set

def addPick(cue, dictionary): # from madlibDict.py '''Prompt for a user response using the cue string, and place the cue-response pair in the dictionary. ''' promptFormat = "Enter a specific example for {name}: " prompt = promptFormat.format(name=cue) response = input(prompt) dictionary[cue] = response

def getUserPicks(cues): '''Loop through the collection of cue keys and get user choices. Return the resulting dictionary. ''' userPicks = dict() for cue in cues: addPick(cue, userPicks) return userPicks

def tellStory(storyFormat): '''storyFormat is a string with Python dictionary references embedded, in the form {cue}. Prompt the user for the mad lib substitutions and then print the resulting story with the substitutions. ''' cues = getKeys(storyFormat) userPicks = getUserPicks(cues) story = storyFormat.format(**userPicks) print(story)

def main(): originalStoryFormat = ''' Once upon a time, deep in an ancient jungle, there lived a {animal}. This {animal} liked to eat {food}, but the jungle had very little {food} to offer. One day, an explorer found the {animal} and discovered it liked {food}. The explorer took the {animal} back to {city}, where it could eat as much {food} as it wanted. However, the {animal} became homesick, so the explorer brought it back to the jungle, leaving a large supply of {food}.

The End ''' tellStory(originalStoryFormat) input("Press Enter to end the program.")

main()