groupby streak of numbers and one row after it

This is my dataframe:

import pandas as pd
df = pd.DataFrame({'a': [1, 1, 1, 0, 1, 0, 1, 1, 0, 0, 1, 1, 0, 0]})

And my desired outcome which is about grouping them is:

    a
0   1
1   1
2   1
3   0

4   1
5   0

6   1
7   1
8   0

10  1
11  1
12  0

Basically, I want to group them by streak of 1 and one row after where streak ends.

For example for the first group I want the first three rows plus the row after it.

I have tried the solutions of these posts: post1, post2.

And also this code:

df.groupby(df.a.diff().cumsum().eq(1))

But it didn’t work.

>Solution :

You can use a reverse cumsum to form the groups:

g = df.loc[::-1, 'a'].eq(0).cumsum()

out = [g for _,g in df.groupby(g, sort=False) if len(g)>1]

Output:

[   a
 0  1
 1  1
 2  1
 3  0,
    a
 4  1
 5  0,
    a
 6  1
 7  1
 8  0,
     a
 10  1
 11  1
 12  0]