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Python Functional Python The Lambda Lambada Recursion

Serhat Bolsu
Serhat Bolsu
15,328 Points
Posted by Serhat Bolsu
Serhat Bolsu
15,328 Points

Recursion in Python Functional Python course, I am really lost in this , and I am also lost in recursions, please help

Recursion in Python Functional Python course, I am really lost in this , and I am also lost in recursions, please help

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()
    reduce(

3 Answers

Paul Bentham
Paul Bentham
24,090 Points
Paul Bentham
Paul Bentham
24,090 Points

Ok, without giving you the answer I'll try and provide a guide:

  • You need to loop through your 'data' (in this instance it would be 'courses').
  • For each 'course' in 'courses' (or data) you need to add the "title" of the prereqs

  • Once you've done that, consider 'course' to be your next set of data that you need to loop through to get the next batch of prereqs, so put that into the prereqs function.

  • Workspaces is your friend on this one, trial and error helps!

Chris Howell's answer here helped me work it out: https://teamtreehouse.com/community/skipping-items-while-building-a-set

Mark Chesney
Mark Chesney
11,747 Points
Mark Chesney
Mark Chesney
11,747 Points

In case a hint is helpful, here's how I got started:

def prereqs(data, pres=None):
    pres = pres or set()
    list_of_dicts = data['prereqs']
    if list_of_dicts:
        pass  # loop over list_of_dicts
    return pres

Tips:

  • It's helpful for me to name the list list_of_dicts according to the datatype.

  • data is courses, which is a dictionary that contains lists of other dictionaries.

    • You can see that as prereqs() is called recursively, data eventually becomes a dict with an empty list for prereqs. When this occurs, the if statement will evaluate to false and not execute.

Good luck!

Alexander Davison
Alexander Davison
65,469 Points
Alexander Davison
Alexander Davison
65,469 Points

Recursion and functional programming is an advanced programming concept, so I wouldn't worry too much about not quite understanding it. I recommend taking a more beginner course before taking this course. (Note that this course is marked as "Advanced")