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Python Python Collections (Retired) Dictionaries Teacher Stats

Challange task 4 of 4 appears bugged, "'Nonetype' has no len()" error

First 3 tasks are running perfectly. However, when I start 4th task it doesn't let code from the first 3 through saying “object of type 'NoneType' has no len()” in the error message. Even if I put 4th function as blank. Oh, and even when I remove all the len() calls with manual for loops for counting.

I tried reloading browser, clearing cookies, re-doing the task, nothing is working :(

# The dictionary will be something like:
# {'Jason Seifer': ['Ruby Foundations', 'Ruby on Rails Forms', 'Technology Foundations'],
#  'Kenneth Love': ['Python Basics', 'Python Collections']}
# Often, it's a good idea to hold onto a max_count variable.
# Update it when you find a teacher with more classes than
# the current count. Better hold onto the teacher name somewhere
# too!
# Your code goes below here.
def most_classes(myDict):
  winrarTeacher = ""
  winrarClasses = 0
  for teacher in myDict.keys():
    numClasses = len(myDict[teacher])
    if numClasses > winrarClasses:
      winrarTeacher = teacher
      winrarClasses = numClasses
  return winrarTeacher

def num_teachers(myDict):
  return len(myDict)

def stats(myDict):
  myList = []
    for item in myDict:
      #myList.append([item, myDict[item]])
      count = 0
      for subItem in myDict[item]:
        count += 1
    fYou = True
  return myList

def courses(myDict):
  allCourses = []
  for item in myDict:

It fixed itself. Error was made because code calls len() on what's returned from 4th function. My code on 4th: def courses(myDict): allCourses = [] for item in myDict: allCourses.extend(myDict[item]) return allCourses

omigod, I got so stressed out and spent 30 minutes in like stress :c / c:

1 Answer

Kenneth Love
Kenneth Love
Treehouse Guest Teacher

Your courses function doesn't return anything. So when the validator calls it, the validator just gets back None, which doesn't have a length.