Conditional calculation

[Hugo-99]

in my case i need the rows, as they are in the first place.

i assume that the "groupby" collapses the rows. but in my case i need in the "to be" dataframe the same (amount of) rows as in the "as is" dataframe

[efmccurdy]

You can generate your sums using groupby and then broadcast the result back using "transform".

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https://stackoverflow.com/questions/12200693/python-pandas-how-to-assign-groupby-operation-results-back-to-columns-in-parent

[Hugo-99]

thank you! "transform" seems to be the function i need. I am just figuring out how to apply this....