Manipulation of a Pandas dataframe most time- and memory-efficiently

Please imagine I have a dataframe like this:

How can I improve this code chunk Visually / Performance wise? [closed]

Closed 3 days ago.

How can I improve this code chunk Visually / Performance wise? [closed]

Closed 3 days ago.

Reset accumulated sum in python, *Hard Mode

I’m trying to reset the accumulation of a sum when a desired condition is met, all in a vectorized manner, without using loops. I’ll first show a simple example and then the real problem.