Welcome to the Treehouse Community

Want to collaborate on code errors? Have bugs you need feedback on? Looking for an extra set of eyes on your latest project? Get support with fellow developers, designers, and programmers of all backgrounds and skill levels here with the Treehouse Community! While you're at it, check out some resources Treehouse students have shared here.

Looking to learn something new?

Treehouse offers a seven day free trial for new students. Get access to thousands of hours of content and join thousands of Treehouse students and alumni in the community today.

Start your free trial

Python Python Collections (Retired) Dictionaries Teacher Stats

Posted by Victor Gavojdea
Victor Gavojdea
11,796 Points

How to get key from value

trying to return the teacher name that has the most classes.

I have a for loop set up that finds the largest list(of classes) and once that's done I want to grab the name of the teacher that it belongs to. But that's where I'm stuck.

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(dict):
  max_count = 0

  for values in dict.values():
    count = len(values)

    if count < max_count:
      continue
    else:
      count = max_count
      winner = dict.key
      continue

  return winner

1 Answer

Chris Freeman
MOD
Chris Freeman
Treehouse Moderator 68,426 Points
Chris Freeman
Chris Freeman
Treehouse Moderator 68,426 Points

Hi Victor, Your current approach only utilizes the values of the dict argument and ignores the keys. There are two ways to get the keys you need.

Method 1: get both the keys and values from the dict using .items()

def most_classes(dict):
  max_count = 0

  for key, values in dict.items():
    count = len(values)

    if count < max_count:
      continue
    else:
      count = max_count
      winner = key
      continue

  return winner

Method 2: get the keys instead of the values from the dict, then access the value using the key. 

def most_classes(dict):
  max_count = 0

  for key in dict:
    count = len(dict[key])

    if count < max_count:
      continue
    else:
      count = max_count
      winner = key
      continue

  return winner

Other feedback:It is common to use singular value instead of plural values in the for statement since you are getting one thing, in this case a list.

Victor Gavojdea
Victor Gavojdea
11,796 Points

Arg! I was so close!! Thank you for the help!