How to calculate an average from average values in a dictionary-CodePudding

I wrote a function to have my dictionary, classes, as my parameter:

def avg(classname):
average = {}
for classnames, grades in classes.items():
    average[classnames] = sum(grades) / len(grades)
print(average)

classes = {"Spanish II": [100, 99, 100, 98], "US History I": [95, 96, 97, 94]}
avg(classes)

It calculates the average of each class from the list, but how would I calculate the average of the averages from all the classes in the dictionary doing it in the function? The two averages are 99.25 and 95.5, as shown in the output:

{'Spanish II': 99.25, 'US History I': 95.5}

So the average of these averages would be 97.375. How would I get my function to print that?

CodePudding user response：

The solution looks very similar to what you've already got:

def average_of_averages(averages):
    output = 0
    for classname, average in averages.items():
        output  = average
    output /= len(averages)
    return output

CodePudding user response：

To get a list of the values in a python dictionary, you can use the method average.values(). Using that, you could write this code to find the average grade of all the classes:

def avg(classname):
    average = {}
    for classnames, grades in classes.items():
        average[classnames] = sum(grades) / len(grades)
    print(average)
    
    list_of_avg_grades = average.items()
    average_grade = sum(list_of_avg_grades) / len(list_of_avg_grades)
    print(average_grade)

classes = {"Spanish II": [100, 99, 100, 98], "US History I": [95, 96, 97, 94]}
avg(classes)

CodePudding user response：

You can take the values of your newly created dictionary using .values and then apply the same logic you applied earlier to get an average of averages.

def avg(classes):
    average = {}
    for classnames, grades in classes.items():
        average[classnames] = sum(grades) / len(grades)
    return average

classes = {"Spanish II": [100, 99, 100, 98], "US History I": [95, 96, 97, 94]}
averages = avg(classes)
#{'Spanish II': 99.25, 'US History I': 95.5}

average_of_averages = sum(averages.values())/len(averages)
#97.375

CodePudding user response：

You're slightly complicating the problem.

All you need is a one liner to solve this (look up list comprehensions)

classes = {'Spanish II': 99.25, 'US History I': 95.5}

def average(class_dict):
    return sum([value for value in class_dict.values()])/len(class_dict)

Let's break the code down to make it more manageable:

[value for value in class_dict.values()]

returns a list of all values in the dictionary. List comprehensions are faster and generally easier to read than a for loop.

sum(list_comprehension)

returns the sum of the values in the list comprehension.

sum/len

returns the average.

CodePudding user response：

you can do everything in one go and have it organized in a dict:

def avg(classes):
    averages = { k: sum(v)/len(v) for k,v in classes.items() } #creates a dict with average of each subject
    return averages | {"course": sum(vals:=averages.values())/len(vals) } #adds and returns the total average

output

{'Spanish II': 99.25, 'US History I': 95.5, 'course': 97.375}

CodePudding user response：

The logic to calculate the average is (value1 value2 value3 ...) / (number of values).

For example, [35, 24, 16] can be caculated as (35 24 16) / 3. So 35 24 16 = 75, and 75 / 3 is 25.