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Python Python Collections (2016, retired 2019) Dictionaries Teacher Stats

Bob Fitzgerald
Bob Fitzgerald
87 Points
Posted by Bob Fitzgerald
Bob Fitzgerald
87 Points

why isn't d.items() working with this challenge?

i tried it first with d.itervalues() but then found that itervalues doens't work with p3, so I tried d.items() in the workspace, it gave me the right answer, but the challenge isn't accepting it...

teachers.py 
# The dictionary will look something like:
# {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'],
#  'Kenneth Love': ['Python Basics', 'Python Collections']}
#
# Each key will be a Teacher and the value will be a list of courses.
#
# Your code goes below here.

def num_teachers(d):
    return len(d)

def num_courses(d):
     print(sum(len(v) for v in d.items()))

1 Answer

andren
andren
28,558 Points
andren
andren
28,558 Points

There are two issues:

  1. You are printing the result rather than returning it

  2. The items method returns both the key and value of each dictionary entry, it does not return just the values like your code seems to assume. The fact that it returns the right output when you pass in the example dictionary is basically just a lucky coincidence, since it's actually counting the wrong thing.

If you use the values method which does return the values of the dictionary like this:

def num_teachers(d):
    return len(d)

def num_courses(d):
     return sum(len(v) for v in d.values())

Then your code will work.