Arithmetic operations on List of Dictionaries in Python - python-3.x

Question

I am currently using Python 3.5.2.
I have a dataset comprising of a list of dictionaries such as below (actual dataset has over 100 such entries):
MyList = [{"Class":1, "ID":123, "Name":"Sam", "Marks":90},
{"Class":1, "ID":124, "Name":"Jack", "Marks":91},
{"Class":1, "ID":125, "Name":"Dan", "Marks":92},
{"Class":2, "ID":234, "Name":"Sammy", "Marks":82},
{"Class":2, "ID":235, "Name":"Jacky", "Marks":85}]
I wanted to get the summary comprising as below:
ClassSummary = [{"Class":1, "TotalStudents": 3, "AvgMarks":91},
{"Class":2, "TotalStudents": 2, "AvgMarks":83.5}]
where TotalStudents refer to count of "Name" in each Class
and AvgMarks refer to Average of "Marks" in each Class.
I am fairly new to list of dictionaries, so any leads on how to approach this would be of great help.
[Edit] Here is what I have tried so far:
class_set = set()
for dict in MyList:
class_set.add(dict["Class"])
This gives me list of different classes available in my List. But I am not sure how to proceed further for subsequent arithmetic operations.
Thanks

Answer 1

It's a bit messy, but here is my solution that works fine:
ClassSummary = []
cls = 0
for d in MyList:
if d["Class"] != cls:
ClassSummary.append({"Class": d["Class"], "TotalStudents": 1, "AvgMarks": d["Marks"]})
cls = d["Class"]
else:
ClassSummary[d["Class"]-1]["TotalStudents"] += 1
ClassSummary[d["Class"]-1]["AvgMarks"] += d["Marks"]
for s in ClassSummary:
s["AvgMarks"] /= s["TotalStudents"]
which gives ClassSummary as:
[{'TotalStudents': 3, 'AvgMarks': 91.0, 'Class': 1}, {'TotalStudents': 2, 'AvgMarks': 83.5, 'Class': 2}]
as you asked for!