Python: How to split values and find averages by category

Question

I am very new to Python and programming, and am struggling to understand a problem. Any help is greatly appreciated.

I have a deque of values and categories:

deque([(3000.0, category1), (6000.0, category1), (8000.0, category2), (3000.0, category3), (7000.0, category3), (4500.0, category3)])

I am trying to use a dictionary to print the average of each value by category. For example, category1 = (3000 + 6000) / 2; category2 = 8000 / 1; category3 = (3000 + 7000 + 4500) / 3.

Is there a straightforward way to do this? So far, my only thought is to create a list of unique categories:

catetory_list = []
for i in deque:
    if i[1] not in category_list:
    category_list.append(i[1])

I think I am missing something important here, but can't seem to find the next step.

I found some similar issues here already, namely here and here, but I am struggling on how to make this fit for my question.

Answer 1

You were close, I think you need to construct a dict, with the values. And then average the values afterwards:

Sample Data:

my_dq = deque([
    (3000.0, 'category1'), (6000.0, 'category1'), (8000.0, 'category2'),
    (3000.0, 'category3'), (7000.0, 'category3'), (4500.0, 'category3')])

Code:

categories = {}
for i in my_dq:
    categories.setdefault(i[1], []).append(i[0])
categories = {k: sum(v) / len(v) for k, v in categories.items()}

Results:

{'category1': 4500.0, 'category3': 4833.3333, 'category2': 8000.0}