Stratified Sampling in Pandas

• Use groupby on the label column to create sub-frames for each label and then use the sample() function.
• Passing an integer gives an exact sample (e.g. sample(5) gives 5 rows).
• Passing frac=0.1 gives a percentage (i.e. 10%)
• Remember to set random_state for reproducible results

df = pd.read_csv("path/to/data.csv")

df.groupby('Category', group_keys=False).apply(lambda x: x.sample(frac=0.1, random_state=42))