How to groupby consecutive values in pandas DataFrame

Question

I have a column in a DataFrame with values:

[1, 1, -1, 1, -1, -1]

How can I group them like this?

[1,1] [-1] [1] [-1, -1]

Answer 1

You can use groupby by custom Series:

df = pd.DataFrame({'a': [1, 1, -1, 1, -1, -1]})
print(df)
   a
0  1
1  1
2 -1
3  1
4 -1
5 -1

print(df['a'].ne(df['a'].shift()).cumsum())
0    1
1    1
2    2
3    3
4    4
5    4
Name: a, dtype: int32

for i, g in df.groupby(df['a'].ne(df['a'].shift()).cumsum()):
    print(i)
    print(g)
    print(g.a.tolist())

1
   a
0  1
1  1
[1, 1]
2
   a
2 -1
[-1]
3
   a
3  1
[1]
4
   a
4 -1
5 -1
[-1, -1]