Question

I am iterating over such objects and creating a list of lists.

Something like this:

#data.py
values = []
for o in objects:
    data = [o.day, o.seconds]
    values.append(data)

So that gives me, for example:

[['27/2', 34], ['23/2', 21], ['25/2', 11], ['27/2', 38]]

But I need to make an additional operation. If data[0] (day) is already in values, I don’t want to append data, I want to add data[1] to the existing object’s data[1].

So from the above list, what I really want is:

[['27/2', 72], ['23/2', 21], ['25/2', 11]]

I can do the operation without a list, but, at the end, I need to convert it to a list for final use.

Answer 1

Here’s how to use a defaultdict

from collections import defaultdict
values = defaultdict(int)
for o in my_object:
    values[o.day] += o.seconds

Here’s a way using a Counter

from itertools import Counter
values = Counter()
for o in my_object:
    values += Counter({o.day: o.seconds})

You can get a list from values like this

values.items() # or list(values.items()) in Python3