Running Counter Within a Groupby Part 2

In [1]:

import numpy as np
import pandas as pd

In [23]:

inventory = pd.Series(["W1","W1","W1","W1","W2","W1"])
Flag = pd.Series([0,0,1,1,0,0])

df=pd.DataFrame([inventory,Flag]).T
df.columns=['Week','Flag']
df

Out[23]:

	Week	Flag
0	W1	0
1	W1	0
2	W1	1
3	W1	1
4	W2	0
5	W1	0

In [24]:

df['G']=df.groupby('Week').Flag.apply(lambda x :(x.diff().ne(0)&x==1)|x==1)

Cntr=df.groupby([df.Week,df.G.cumsum()]).G.apply(lambda x : (~x).cumsum())
df['Cntr']=Cntr
df

Out[24]:

	Week	Flag	G	Cntr
0	W1	0	False	1
1	W1	0	False	2
2	W1	1	True	0
3	W1	1	True	0
4	W2	0	False	1
5	W1	0	False	1