Why len(dictionary.values()) cause TypeError?

Question

I really stack on this Challenge Task so I need your help.

Question is this.

"Create a function named most_courses. most_courses should return the name of the teacher with the most courses. You might need to hold onto some sort of max count variable."

Example input is this.

"{'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'], 'Kenneth Love': ['Python Basics', 'Python Collections']}"

So Answer should be

'Andrew Chalkley', 'Kenneth Love'

So I make def most_courses like this. But it returns as TypeError 'int' object is not iterable.

def most_courses(arg_5):
    k=list(arg_5.keys())
    v=list(len(arg_5.values()))
    return k[v.index(max(v))]

I dont understand what makes an Error. I expect this one returning the list of [2, 2] because there are 2 values on each dictionary.

v=list(len(arg_5.values()))

I appreciate if you explain some hint or answer to this task.

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(arg):
    return len(arg)

def num_courses(arg_1):
  list1 = []
  for arg_2 in arg_1.values():
    list1.extend(arg_2)
  return (len(list1))

def courses(arg_3):
    list2 = []
    for arg_4 in arg_3.values():
        list2.extend(arg_4)
    return (list2)

def most_courses(arg_5):
    k=list(arg_5.keys())
    v=list(len(arg_5.values()))
    return k[v.index(max(v))]

Answer 1 · 2018-01-02T16:31:16Z

January 2, 2018 4:31pm

This one tripped me up when I was going through this course. The main issue you are having is "I dont understand what makes an Error. I expect this one returning the list of [2, 2] because there are 2 values on each dictionary." You are correct in that you can see two items for each person. ['jQuery Basics', 'Node.js Basics'] for Andrew Chalkley and ['Python Basics', 'Python Collections'] for Kenneth Love. However the way .values() is working is not how you expect it to. What .values() is doing is it is getting all of the values for Andrew and all of the values for Kenneth and lumping them into two distinct lists. When you do .values() on the dictionary in teachers.py you get this result.

dict_values([['Python Basics', 'Python Collections'], ['jQuery Basics', 'Node.js Basics']])

When you run len(example_dictionary_from_teachers.values()) you are getting the result 2. (I did not use arg_5 because Kenneth said the dictionary would look something like the one above so he might be tricking you with a longer/shorter dictionary.) What is happening with the len() is len checks and finds [['Python Basics', 'Python Collections'], ['jQuery Basics', 'Node.js Basics']] being a single list. len then looks in the list and finds one item ['Python Basics', 'Python Collections'] then two items ['jQuery Basics', 'Node.js Basics'] so it returns a result of 2.

This messes up your list() in list(len(example_dictionary_from_teachers.values())) because you cannot turn the integer 2 into a list. Let us know if you have any more questions or need some clarification on anything.

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Why len(dictionary.values()) cause TypeError?

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Zachary Jackson

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Zachary Jackson

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