Create new column on pandas DataFrame in which the entries are randomly selected entries from another column - pandas

Question

I have a DataFrame with the following structure.
df = pd.DataFrame({'tenant_id': [1,1,1,2,2,2,3,3,7,7], 'user_id': ['ab1', 'avc1', 'bc2', 'iuyt', 'fvg', 'fbh', 'bcv', 'bcb', 'yth', 'ytn'],
'text':['apple', 'ball', 'card', 'toy', 'sleep', 'happy', 'sad', 'be', 'u', 'pop']})
This gives the following output:
df = df[['tenant_id', 'user_id', 'text']]
tenant_id user_id text
1 ab1 apple
1 avc1 ball
1 bc2 card
2 iuyt toy
2 fvg sleep
2 fbh happy
3 bcv sad
3 bcb be
7 yth u
7 ytn pop
I would like to groupby on tenant_id and create a new column which is a random selection of strings from the user_id column.
Thus, I would like my output to look like the following:
tenant_id user_id text new_column
1 ab1 apple [ab1, bc2]
1 avc1 ball [ab1]
1 bc2 card [avc1]
2 iuyt toy [fvg, fbh]
2 fvg sleep [fbh]
2 fbh happy [fvg]
3 bcv sad [bcb]
3 bcb be [bcv]
7 yth u [pop]
7 ytn pop [u]
Here, random id's from the user_id column have been selected, these id's can be repeated as "fvg" is repeated for tenant_id=2. I would like to have a threshold of not more than ten id's. This data is just a sample and has only 10 id's to start with, so generally any number much less than the total number of user_id's. This case say 1 less than total user_id's that belong to a tenant.
i tried first figuring out how to select random subset of varying length with
df.sample
new_column = df.user_id.sample(n=np.random.randint(1, 10)))
I am kinda lost after this, assigning it to my df results in Nan's, probably because they are of variable lengths. Please help.
Thanks.

Answer 1

per my comment:
Your 'new column' is not a new column, it's a new cell for a single row.
If you want to assign the result to a new column, you need to create a new column, and apply the cell computation to it.
df['new column'] = df['user_id'].apply(lambda x: df.user_id.sample(n=np.random.randint(1, 10))))
it doesn't really matter what column you use for the apply since the variable is not used in the computation