How to make count the amount between 2 conditions?-CodePudding

When the start column is true, start counting.

When the end column is true, stop counting.

Input:

import pandas as pd
df=pd.DataFrame()
df['start']=[False,True,False,False,False,True,False,False,False]
df['end']=  [False,False,False,True,False,False,False,True,False]

Expected Output:

    start   end expected
0   False   False   0
1   True    False   1
2   False   False   2
3   False   True    0
4   False   False   0
5   True    False   1
6   False   False   2
7   False   True    0
8   False   False   0

CodePudding user response：

You can use cumsum to compute the groups, groupby.cummax to identify the values after a start (and later mask with where) and groupby.cumcount to increment a counter:

# make groups between start/end
group = (df['start']|df['end']).cumsum()
# identify values after a start and before an end
mask = df['start'].groupby(group).cummax()

# compute a cumcount and mask with the above "mask"
df['expected'] = df.groupby(group).cumcount().add(1).where(mask, 0)

Output:

   start    end  expected
0  False  False         0
1   True  False         1
2  False  False         2
3  False   True         0
4  False  False         0
5   True  False         1
6  False  False         2
7  False   True         0
8  False  False         0