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Python Functional Python The Lambda Lambada Recursion

Posted by Victor Gavojdea
Victor Gavojdea
11,796 Points

stepping into tuples

I don't know how to step into the nested 'prereqs' tuple to grab any of the titles, much less have it give me the 2nd one. I don't think Kenneth went over this in any of the videos prior to this. I hope I missed something. Very lost. Looking for help.

courses.py 
from operator import add

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()
    if data.prereqs == None
    #add(set, title)
    #return prereqs(

2 Answers

Julian Garcia
Julian Garcia
18,380 Points
Julian Garcia
Julian Garcia
18,380 Points

It is a little tricky, because they never ask for example that you don't need include Django Basics. But if I think about it, it is not a prerequisite.

The solution I found was:

def prereqs(data, pres=None):
    pres = pres or set()
    if isinstance(data, list): 
        for item in data:    #Sweep the list
            pres.add(item['title'])  #Add current item title
            prereqs(item['prereqs'], pres) # The inner prereq are process in a recursive call to this method
    else:
        pres = prereqs(data['prereqs'], pres) #This is the initial point, Django Basics's prereqs, but this is not included in the answer                
                                                #We din't include data['title']
  return pres

This code gives result in my terminal :

 Flask Basics
 Python Basics
 Setting Up a Local Python Environment
 Object-Oriented Python
 Python Collections
Victor Gavojdea
Victor Gavojdea
11,796 Points

Thank you for the help. So then does item go down the tree? I thought it would stay at the first level.

Julian Garcia
Julian Garcia
18,380 Points
Julian Garcia
Julian Garcia
18,380 Points

The result is presented unordered that is because set is an unordered collection of unique elements. For example, if you put and text item in the set and continue adding more items and then you print the content of that set , the elements are not in the order you put it there.