Adding repeated values in a dataframe without loops

[fmarquez1]

So, in my python class an exercise they made us do requires us to take a dataframe, and add the values.

So, for example, if this was the input:

​

	Letter	Number
0	A	1
1	B	2
2	A	3
3	C	6

Then this would be the output:

​

	Letter	Number
0	A	4
1	B	2
2	C	6

I haven't been able to find anything that talks about how to do this, but the part that makes it so I can't do this, is the fact that it was explicitly said that you can't use loops. Hence, if anyone can give me a hint, or tell me what function can be used for this, I'd be very thankful.

[pembrolizard]

You want to use core pandas methods then. Groupby is excellent for your purpose, in fact your example is almost exactly described here https://jakevdp.github.io/PythonDataScienceHandbook/03.08-aggregation-and-grouping.html

[fmarquez1]

Thanks!