I have a pandas dataframe with the format:

I want to update it such that the group number is one plus the previous group number only if the condition is true:

What is the most pythonic way to do this? Is using a loop easiest, or is there a more efficient or readable way with pandas?

CodePudding user response：

This is cumsum:

 s = df['Condition'].cumsum()
 df['Group'] = s - s.min()