Code that appears to work doesn't

Question

So, in task two the num_courses function seems to return 4 if i use the dict in the comment, which i assume is correct. but it doesnt pass the task.

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(arg1):
    count = 0
    for items in arg1.keys():
        count += 1
    return count

def num_courses(arg1):
    out = 0 
    for items in arg1.keys():
        for v in items:
            out += 1
    return out

Answer 1 · 2018-05-02T05:50:18Z

May 2, 2018 5:50am

Hi Rob,

The .keys() method on an iterable will return a list of keys. So when you write:

for items in arg1.keys():

your for loop will iterate through ['Andrew Chalkley', 'Kenneth Love']. Accordingly, during the first iteration of that loop, items will have the value 'Andrew Chalkley'. Then when you do a for loop on 'Andrew Chalkley', it's going to iterate through the characters in 'Andrew Chalkley' and increment your counter every time you get a new character.

To correctly use the method you are trying to use, you would need to remember that your outer loop is going to be a series of keys. Then in your inner loop you can use that key to index back into the iterable to get the value. E.g.,:

for key in some_dictionary.keys():
    for element in some_dictionary[key]:
        print(element)

If this seems a bit long-winded, you're right. There is a better way, and that's to use .items() instead of .keys(). With .items() you get back a list of tuples where the first element in each tuple is the key and the second is the value. This means you can structure your for loop as follows:

for key, value in some_dictionary.items():
   print(key)
   print(value)

Hope this helps

Cheers

Alex

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rob bert

rob bert

Code that appears to work doesn't

1 Answer

Alex Koumparos

Alex Koumparos