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Python

Posted by Y B
Y B
14,136 Points

append give me 'None' list?

working through the collections part of the python course and the teacher dict question however when I try to answer the stats question with:

def stats(dct): 7 total_list = [] 8 number = 0 9 for tutor,course in dct.items(): 10 number = len(course) 11 sublist = [tutor,number] 12 total_list = total_list.append(sublist) 13 return total_list

line 12 seems to keep wiping total_list to make it have 'None'

I have no idea why?

Thanks.

4 Answers

Mikael Enarsson
Mikael Enarsson
7,056 Points

Your code seems fine (maybe not how I would do it, but that's ok), except for one thing:

In your code, you have the line

total_list = total_list.append(sublist)

Now, it's good that you are using append here, however, you don't need the "total_list = " part. Append odds the item in the parentheses directly. A working solution would look like this (tested):

def stats(dct):
  total_list = []
  number = 0
  for tutor,course in dct.items():
    number = len(course)
    sublist = [tutor,number]
    total_list.append(sublist)
  return total_list

Also, for future reference, please have a look at the Markdown Cheatsheet, especially for when you want to post code. It makes your question easier to read and allows us to answer more quickly ^^

Y B
Y B
14,136 Points
Y B
Y B
14,136 Points

Thanks but unfortunately the answer still isn't accepted - not sure why:

# 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(dct):
  classes = 0
  teacher = ""
  for tutor,courses in dct.items():
    if len(courses) > classes:
      classes = len(courses)
      teacher = tutor
  return teacher

def num_teachers(dct):
  return len(dct)

def stats(dct):
  total_list = []
  number = 0
  for tutor,course in dct.items():
    number = len(course)
    total_list.append([tutor,number]) 
    return total_list

??

Mikael Enarsson
Mikael Enarsson
7,056 Points
Mikael Enarsson
Mikael Enarsson
7,056 Points

You have to much indentation on the return:

def stats(dct):
  total_list = []
  number = 0
  for tutor,course in dct.items():
    number = len(course)
    total_list.append([tutor,number]) 
    return total_list     #returns total_list at the end of the first pass of the loop (meaning that it only sends back a list with the first teacher/number of courses

You have to have your return after the loop, like this:

def stats(dct):
  total_list = []
  number = 0
  for tutor,course in dct.items():
    number = len(course)
    total_list.append([tutor,number])   #Jumps back to the top of the loop from here
  return total_list    #After the loop has gone through every teacher in the dict, return total_list

It's a subtle thing, but it works ^^

Y B
Y B
14,136 Points
Y B
Y B
14,136 Points

Wow I'm an idiot, thanks - I had been looking at it much too long and had missed the obvious things.
Thanks.