Add elements from list to new data frame column based on condition

Question

I have this dataframe:

id1	id2
2341	qw123
2321	-
-	de121
2341	qd111

And I want to add 3rd column id3 with randomly generated ids in a list:

['11231', '123141', '234512']

The thing that makes it difficult to me is how to attach the same random id from the list to each row where id1 is the same.

For example the output file should look like this:

id1	id2	id3
2341	qw123	11231
2321	-	123141
-	de121	234512
2341	qd111	11231

Any solution is appreciated!

Answer 1

You can create a dict for mapping the unique id1 keys to the random numbers. Then use .map() to map id1 values to these random numbers for assignment to new column id3 , as follows:

num_list = ['11231', '123141', '234512']
id1_unique = df['id1'].unique()

m_dict = dict(zip(id1_unique,  np.random.choice(num_list, len(id1_unique))))

df['id3'] = df['id1'].map(m_dict)