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Python Python Collections (Retired) Dictionaries Teacher Stats

Posted by veggie mustache
veggie mustache
9,990 Points

Why does this only work some times?

This will past every third time or so. What am I doing wrong?

teachers.py 
# 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(teachers):
  max_count = 0
  busiest_teacher = ''
  for teacher in teachers:
    if len(teachers.values()) > max_count:
      max_count = len(teachers.values())
      busiest_teacher = teacher
  return busiest_teacher

3 Answers

Ryan Merritt
Ryan Merritt
5,789 Points
Ryan Merritt
Ryan Merritt
5,789 Points 
teachers.values()

will return a list of all values in the dictionary, not the value of a particular key. Hint: use the teacher variable to access the value of that particular teacher from the dict.

veggie mustache
veggie mustache
9,990 Points
veggie mustache
veggie mustache
9,990 Points

Thank you. It worked. Why does it work some of the time? Dumb luck depending on the list?

Ryan Merritt
Ryan Merritt
5,789 Points
Ryan Merritt
Ryan Merritt
5,789 Points

Consider the following lines of code I inputted into the python interpreter:

>>> teachers = {'Jason Seifer': ['Ruby Foundations', 'Ruby on Rails Forms', 'Technology Foundations'], 'Kenneth Love': ['Python Basics', 'Python Collections']}
>>> teachers.values()
dict_values([['Ruby Foundations', 'Ruby on Rails Forms', 'Technology Foundations'], ['Python Basics', 'Python Collections']])

When I asked python for teachers.values() it returns every value in the dictionary, which in this case is comprised of two lists.

Now consider:

>>> for teacher in teachers:
...   print(len(teachers.values()))
... 
2
2
>>> for teacher in teachers:
...   print(len(teachers[teacher]))
... 
3
2

The first loop loops through the items of the dict (it loops twice because there are two items), then prints out the number of total values TWICE. Note that this is the length of every value in the dict, NOT the length of the list inside a dict item.

The second loop also loops twice (for each item in the dict), but instead prints out the length of teachers[teacher].

I have yet to have my evening cup of coffee so forgive the potentially confusing response :D

veggie mustache
veggie mustache
9,990 Points
veggie mustache
veggie mustache
9,990 Points

Great! Thanks! This really helped for the 4th part too :-)