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Python Python Collections (Retired) Dictionaries Teacher Stats

Posted by Matt Staten
Matt Staten
1,630 Points

A more "pythonic" approach to solving this challenge?

I have passed the "Teacher Stats" challenge using the code attached to this question, but I can't help but wonder if there's a more "pythonic" way to achieve the same result.

For instance, most_classes() and my_dict() both have loops within loops, which is a fairly poor algorithmic technique. If we were using larger datasets, these would run slowly.

My understanding of Python is that things should be done with the fewest system calls possible, aiming for system efficiency over necessary code readability. Am I mistaken in this understanding?

teachers.py 
def most_classes(my_dict):
    max_count = 0
    busiest_teacher = ''
    for key in my_dict:
        if len(my_dict[key]) > max_count:
            max_count = len(my_dict[key])
            busiest_teacher = key
            continue
        else:
            continue
    return busiest_teacher

def num_teachers(my_dict):
    return len(my_dict)

def stats(my_dict):
    list_of_teachers = []
    for key in my_dict:
        my_str = [key, len(my_dict[key])]
        list_of_teachers.append(my_str)
    return list_of_teachers

def courses(my_dict):
    list_of_classes = []
    for key in my_dict:
        for value in my_dict[key]:
            list_of_classes.append(value)
    return list_of_classes

2 Answers

Kenneth Love
STAFF
Kenneth Love
Treehouse Guest Teacher
Kenneth Love
Kenneth Love
Treehouse Guest Teacher

Your code isn't bad Python code at all. You don't need those continues (or the else: clause) but that's effectively a no-op anyway. You could leave off my_str on the stats() function and just append the new list directly. And then you can use .extend() instead of that second for loop and .append() in the courses() function.

Other than those fairly small changes, there's not much to be make "more Pythonic".

Kenneth Love
Kenneth Love
Treehouse Guest Teacher
Kenneth Love
Kenneth Love
Treehouse Guest Teacher

Also, Python is all about readability. I'd rather have code I can read and follow the first time through than code that makes 1 or 2 fewer loops or function calls. The efficiency comes in at the end, when it matters most. Remember, we're gonna compile down to byte code anyway, so cutting out that function probably saves you less than a millisecond in actual execution time. But how much time does it cost the next person (yourself included) that reads the code?

Charlie L.
Charlie L.
10,120 Points
Charlie L.
Charlie L.
10,120 Points

Python should be clean and clear. Your code does both pretty well. There are ways you could improve it if you wanted to.

For example:

def courses(my_dict):
    list_of_classes = []
    for key in my_dict:
        for value in my_dict[key]:
            list_of_classes.append(value)
    return list_of_classes

Could be changed to:

def courses(my_dict):
    list_of_classes = []
    for key, value in my_dict:
        list_of_classes.append(value)
    return list_of_classes
Kenneth Love
Kenneth Love
Treehouse Guest Teacher
Kenneth Love
Kenneth Love
Treehouse Guest Teacher

I think you mean .extend() not .append(). Using .append() will produce a list of lists.