Dictionaries in dictionaries

[nilamo]

for i in data:
    myDict[i[0]] = {i[1]: i[2]}

Instead of setting the dict's value to a dict, set the sub-dict's value, and then make sure there's a sub-dict you can access. Also, use better variable names lol

for key, sub_key, value in data:
    if key not in myDict:
        myDict[key] = {}
    myDict[key][sub_key] = value

Also...

data = list(map(lambda x: x.split(), fin.readlines()))

You can use str.split directly:

data = list(map(str.split, fin.readlines()))