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Python Python Collections (Retired) Dictionaries Teacher Stats

Mona Jalal
Mona Jalal
4,302 Points
Posted by Mona Jalal
Mona Jalal
4,302 Points

most_classes() returns the wrong teacher

I passed it first but in the new challenge the method most_classes() is not passing now:

def num_teachers(dict): return len(dict)

def most_classes(dict): for item in dict: count = 0 max = 0 teacher = None for course in dict[item]: count += 1 if count > max: max = count teacher = item return teacher

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.
# 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 num_teachers(dict):
    return len(dict)

def most_classes(dict):
    for item in dict:
        count = 0
        max = 0
        teacher = None
        for course in dict[item]:
            count += 1
        if count > max:
            max = count
            teacher = item
    return teacher

7 Answers

jcorum
jcorum
71,830 Points

Mona, some folk think we shouldn't provide real answers, but only hints, but I'm of the opinion that you learn better if you don't get too frustrated, and can see the answer once you've tried and it hasn't worked. At least that's been my experience.

If you are of a different persuasion about this then don't read on! In other words, spoiler alert.

def most_classes(teacher_dict):
  max_count = 0
  teacher = ''
  for key in teacher_dict:
    value = teacher_dict[key]
    if len(value) > max_count:
      max_count = len(value)
      teacher = key
  return teacher

def num_teachers(teacher_dict):
  teacher_count = 0
  for key in teacher_dict:
    teacher_count += 1
  return teacher_count

def stats(teacher_dict):
  teacher_count_list = []
  for key, value in teacher_dict.items():
      newItem = [key, int(len(value))]
      teacher_count_list.append(newItem)
  return teacher_count_list

def courses(teacher_dict):
  course_list = []
  for key, value in teacher_dict.items():
    new_list = value;
    for newItem in new_list:
      course_list.append(newItem)
  return course_list
jcorum
jcorum
71,830 Points
jcorum
jcorum
71,830 Points

You enter a blank line, then you hit the accent grave key 3 times ``` and the type of code, so you'd put python, then the code on the next line(s), followed by a line with 3 more accent graves ``` and then a blank line. 

def most_classes(dict): 
    max=0 
    teacher=None 
    for key in dict: 
        if len(dict[key]) > max: 
            max=len(dict[key]) 
            teacher=key 
    return teacher

There are more instructions in the Markdown Cheatsheet below, but that's the main part for including code.

jcorum
jcorum
71,830 Points
jcorum
jcorum
71,830 Points

There's a question on StackOverflow about whether Python has generics like Java, and here's part of the answer:

"No. Python is not a statically typed language, so there is no need for them. Java generics only provide compile time type safety; they don't do anything at runtime. Python doesn't have any compile time type safety, so it wouldn't make sense to add generics to beef up the compile time type checks Python doesn't have.

A list, for example, is an untyped collection. There is no equivalent of distinguishing between List<Integer> and List<String> because a Python list can store any type of object."

http://stackoverflow.com/questions/20449398/does-python-have-generic-methods

But that's not quite the right answer. See: https://www.python.org/dev/peps/pep-0484/#generics

However, that's way beyond the Python track.

Here are some examples of how to create and work with lists:

a_list = list(range(10))
a_list = a_list + [10, 11, 12]

a_list.append([13, 14, 15])
//a_list will be [1...9, 10, 11, 12, [13, 14, 15])

list_1 = [1,2,3]
list_2 = [4,5,6]
list_3 = list_1  + list_2
Mona Jalal
Mona Jalal
4,302 Points
Mona Jalal
Mona Jalal
4,302 Points

for num_teachers you could only use def num_teachers(dict): return len(dict) jcorum

jcorum
jcorum
71,830 Points
jcorum
jcorum
71,830 Points

Hey, that's right. Someone else asked how to do it in a loop (for practice) and I forgot I'd changed it. Good eye.

Mona Jalal
Mona Jalal
4,302 Points
Mona Jalal
Mona Jalal
4,302 Points

Also I solved it this way too: How should I select something as code? jcorum 

python
def most_classes(dict):
    max=0
    teacher=None
    for key in dict:
        if len(dict[key]) > max:
            max=len(dict[key])
            teacher=key
    return teacher
Mona Jalal
Mona Jalal
4,302 Points
Mona Jalal
Mona Jalal
4,302 Points

ok thank you so much. I don't know how to create a separate thread so I ask it here as googling didn't help. How can I create a list of list in Python and assign a value to it? in Java: jcorum 

List<List<Integer>>  list = new ArrayList<>();
list.get(0).add(1);