Get the average of dictionary values?

Question

I have the following dictionary:

StudentGrades = {
    'Ivan': [4.32, 3, 2],
    'Martin': [3.45, 5, 6],
    'Stoyan': [2, 5.67, 4],
    'Vladimir': [5.63, 4.67, 6]
}

I want to make a function that prints the average of the grades of the students, i.e. the average of the values

Answer 1

This answer was intended for Python2, which is now dead

Okay, so let's iterate over all dictionary keys and average the items:

avgDict = {}
for k,v in StudentGrades.iteritems():
    # v is the list of grades for student k
    avgDict[k] = sum(v)/ float(len(v))

In Python3, the iteritems() method is no longer necessary, can use items() directly.

now you can just see :

avgDict
Out[5]: 
{'Ivan': 3.106666666666667,
 'Martin': 4.816666666666666,
 'Stoyan': 3.89,
 'Vladimir': 5.433333333333334}

---

From your question I think you're queasy about iteration over dicts, so here is the same with output as a list :

avgList = []
for k,v in StudentGrades.iteritems():
    # v is the list of grades for student k
    avgDict.append(sum(v)/ float(len(v)))

Be careful though : the order of items in a dictionary is NOT guaranteed; this is, the order of key/values when printing or iterating on the dictionary is not guaranteed (as dicts are "unsorted"). Looping over the same identical dictionary object(with no additions/removals) twice is guaranteed to behave identically though.