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Python Functional Python The Lambda Lambada Recursion

Posted by Emily Strobl
Emily Strobl
5,429 Points

Dont know what to do

Challenge: Finish the prereqs function so that it recursively finds all of the prerequisite course titles in courses (like "Object-Oriented Python" is a prerequisite for "Django Basics"). You should add() the title of the prerequisite to the pres set and then call prereqs again with the child courses.

In the end, return the prereqs set.

courses.py 
courses = {'count': 2,
           'title': 'Django Basics',
           'prereqs': [{'count': 3,
                     'title': 'Object-Oriented Python',
                     'prereqs': [{'count': 1,
                               'title': 'Python Collections',
                               'prereqs': [{'count':0,
                                         'title': 'Python Basics',
                                         'prereqs': []}]},
                              {'count': 0,
                               'title': 'Python Basics',
                               'prereqs': []},
                              {'count': 0,
                               'title': 'Setting Up a Local Python Environment',
                               'prereqs': []}]},
                     {'count': 0,
                      'title': 'Flask Basics',
                      'prereqs': []}]}


def prereqs(data, pres=None):
    pres = pres or set()

1 Answer

Steven Parker
Steven Parker
231,248 Points
Steven Parker
Steven Parker
231,248 Points

Try breaking the task down to more easily identifiable/implementable parts:

  • loop through the list of "prereqs" in the data
  • add the title of each prerequisite to the "pres" set
  • now use recursion to get the prerequisites of the other prerequisites
  • do this by using the function to call itself and pass the "prereqs" as data and the "pres" as the set