python - Sorting a dictionary by average of list in value -

i have dictionary keys names , values lists of 3 integers (these scores of named people):

classscores={     'bob':[1, 6, 3],     'jim':[6, 10, 3],     'fred':[0, 2] } 

i need print sorted average of scores (highest first). have created working code this:

classaverages={} student in classscores:     classaverages[student]=sum(classscores[student])/len(classscores[student]) student in sorted(classaverages, key=classaverages.get, reverse=true):     print(student, "average:", sum(classscores[student])/len(classscores[student])) 

however, feel inefficient uses 2 for loops has go through every student twice. therefore looking suggestions incorporate sorting 2nd loop (presumably sorted function).

update: i've gone lambda, have defined before for loop can use print averages:

classaverages=lambda student: sum(classscores[student]) / len(classscores[student]) student in sorted(classscores, key=classaverages, reverse=true):     print(student, "average:", classaverages(student)) 

you can calculate average per student in key function:

for student in sorted(classscores, key=lambda k: sum(classscores[k]) / len(classscores[k]), reverse=true): 

using 2 loops marginally less efficient however; increased fixed cost per student determine order. missed opportunity re-use average in second loop when displaying averages:

classaverages={} student in classscores:     classaverages[student] = sum(classscores[student]) / len(classscores[student])  student in sorted(classaverages, key=classaverages.get, reverse=true):     print(student, "average:", classaverages[student]) 

you loop on dictionary items in generator expression calculate averages, sort on averages, , display calculated average in 1 operation:

student_averages = ((sum(scores) / len(scores), s) s, scores in classscores.items())  average, student in sorted(student_averages, reverse=true):     print(student, "average:", average) 

the generator produces data in (average, student) pairs ease sorting (we don't need key pick out second value).