Sample each group after pandas groupby

Question

I know this must have been answered some where but I just could not find it.

Problem: Sample each group after groupby operation.

Answer 1

pandas >= 1.1: GroupBy.sample

This works like magic:

# np.random.seed(0)
df.groupby('b').sample(frac=.3) 

   a  b
5  6  0
0  1  1

---

pandas <= 1.0.X

You can use GroupBy.apply with sample. You do not need to use a lambda; apply accepts keyword arguments:

df.groupby('b', group_keys=False).apply(pd.DataFrame.sample, frac=.3)

   a  b
5  6  0
0  1  1