code working on my computer, but can not submit task

Question

the code in teachers.py is working perfectly well on my computer though when i press check work, I get the "Try again!" message the function that was added is most_courses

teachers.py

# The dictionary will look something like:
# {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics'],
#  'Kenneth Love': ['Python Basics', 'Python Collections']}
#
# Each key will be a Teacher and the value will be a list of courses.
#
# Your code goes below here.
def num_teachers(dic):
    return len(dic)

def num_courses(dic):
    l = 0
    for t in dic:
        l += len(dic[t])
    return l

def courses(dic):
    l = list()
    for t in dic:
        l.extend(dic[t])
    return l

def most_courses(dic):
    for t in dic:
        dic[t] = len(dic[t])
    return (list(dic.keys())[list(dic.values()).index(sorted(list(dic.values()))[-1])])

Answer 1 · 2017-10-29T01:10:08Z

October 29, 2017 1:10am

You've asked a good question!

Try running your code twice:

# define a dictionary 
courses = {'Andrew Chalkley': ['jQuery Basics', 'Node.js Basics', 'B', 'C'],
       'Kenneth Love': ['Python Basics', 'A', 'Python Collections']}
# first run
print(most_courses(courses))
# second run
print(most_courses(courses))

# this yields the results 

Andrew Chalkley
Traceback (most recent call last):
  File "<string>", line 33, in <module>
  File "<string>", line 25, in most_courses
TypeError: object of type 'int' has no len()

Explanation: Python passes function arguments using reference pointers. When the code

        dic[t] = len(dic[t])

is run during the first execution, the original dict courses is altered by replacing the list of courses with an integer.

During the second run, the dict values are now all integers.

When working with dictionaries as parameters, it is important not to alter them unless, in the unusual case, it is intentional.

Post back if you need more help. Good luck!!!

Answer 2 · 2017-10-29T02:37:46Z

October 29, 2017 2:37am

Thank you very much for the detailed explanation. Now when I know that it can run few time in background during check, it's perfectly clear. I was assuming that it will run only once and intentionally altered the dictionary due to laziness to create and handle another variable.

I'm wondering if you can help me to understand another issue: here it the code for the first 3 steps:

def num_teachers(dic):
    return len(dic)

def num_courses(dic):
    l = 0
    for t in dic:
        l += len(dic[t])
    return l

def courses(dic):
    t = list()
    for t in dic:
        t.extend(dic[t])
    return t

while passing on it's own, it was not important what I tried to use later would fail. And I had quite a few versions of the most_courses(). Replacing the courses() function with another version that does it in a slightly different way, it was was solved. here is a sample of the courses() that didn't prevent the code to work:

def courses(dic):
    t = []
    for i in dic.values():
        t.extend(i)
    return t

any idea what went wrong ?

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Dmitri Weissman

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code working on my computer, but can not submit task

Dmitri Weissman

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2 Answers

Chris Freeman

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Dmitri Weissman

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