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Python Functional Python The Lambda Lambada Recursion

Denis Silva
Denis Silva
3,962 Points
Posted by Denis Silva
Denis Silva
3,962 Points

No clue on how to solve this problem

I got no clue on how could I start solving this problem, should I use reduce ? and when it says add(), should I print how many prerequisites are or print all titles ?

Thanks in advance.

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()
Denis Silva
Denis Silva
3,962 Points
Denis Silva
Denis Silva
3,962 Points

Problem guidelines:

""" 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. """

1 Answer

Joshua Yoerger
Joshua Yoerger
11,206 Points
Joshua Yoerger
Joshua Yoerger
11,206 Points

The challenge wants a list of prerequisite titles (with no duplicates, but that is taken care of by the set object automatically). You want to use the add() method on the set pres like so:

pres.add(prereq_course['title'])

You certainly can use reduce(), but it is also possible to solve the challenge without it. Try to think of a way to recursively iterate over the entire "tree" of course dependencies adding a title whenever the function is "pointing at" a new prereq. If you get stuck, check out some of these answers: https://teamtreehouse.com/community/code-challenge:9022 Good luck!