Block randomization using python?

Question

I have the following input table (df):

ColumnA	ColumnB	Blocks
A	12	1
B	32	1
C	44	1
D	76	2
E	99	2
F	123	2
G	65	2
H	87	3
I	76	3
J	231	3
k	80	4
l	55	4
m	27	5
n	67	5
o	34	5

I would like to perform block randomization such that, it pick one value from each blocks ( one value from 1,2,3,4,5) and create that as a separate table.

The output should look something like the following:

ColumnA	ColumnB	Blocks	Groups
B	32	1	A1
E	99	2	A1
I	76	3	A1
l	55	4	A1
m	27	5	A1
A	12	1	A2
F	123	2	A2
k	80	3	A2
m	27	4	A2
n	67	5	A2
C	44	1	A3
H	87	2	A3
J	231	3	A3
n	67	4	A3
o	34	5	A4
D	76	1	A4
G	65	2	A4

Randomly selected rows such that each group has all the blocks (evenly distributed).

What I tried so far?

df = df.groupby('blocks').apply(lambda x: x.sample(frac=1,random_state=1234)).reset_index(drop=True)
treatment_groups = [f"A{i}" for i in range(1, n+1)]
df['Groups'] = (df.index // n).map(dict(zip(idx, treatment_groups)))

This doesn't randomize according to the blocks column. How do I do that?

Answer 1

Let us try by defining a function to generate random samples from each block:

def random_samples(n):
    for i in range(1, n+1):
        for _, g in df.groupby('Blocks'):
            yield g.sample(n=1).assign(Groups=f'A{i}')

sampled = pd.concat(random_samples(4), ignore_index=True)

---

>>> sampled

   ColumnA  ColumnB  Blocks Groups
0        A       12       1     A1
1        D       76       2     A1
2        I       76       3     A1
3        k       80       4     A1
4        n       67       5     A1
5        C       44       1     A2
6        G       65       2     A2
7        J      231       3     A2
8        l       55       4     A2
9        m       27       5     A2
10       B       32       1     A3
11       G       65       2     A3
12       H       87       3     A3
13       l       55       4     A3
14       m       27       5     A3
15       B       32       1     A4
16       F      123       2     A4
17       I       76       3     A4
18       l       55       4     A4
19       m       27       5     A4