Python : expand dataframe column value based on an other column [duplicate]

Question

I have a dataframe that looks like :

GroupID | Name
 1      | aaa
 2      | 
 2      | bbb
 1      | 
 1      |

The idea would be to expand all Name values to every line with the same GroupID :

GroupID | Name
 1      | aaa
 2      | bbb
 2      | bbb
 1      | aaa
 1      | aaa

How would I do that easily ?

df.groupby("GroupID")["Name"].bfill().ffill()

Erfan
– Erfan

2021-06-15 09:08:06 +00:00
Commented Jun 15, 2021 at 9:08 — Erfan
– Erfan, Commented Jun 15, 2021 at 9:08

Andreas · Accepted Answer · 2021-06-15 09:14:13Z

1

You could use a dictionary:

dct = dict(df[~df['Name'].isna()].values)
df['Name'] = df['GroupID'].replace(dct)

   GroupID Name
0        1  aaa
1        2  bbb
2        2  bbb
3        1  aaa
4        1  aaa

answered Jun 15, 2021 at 9:14

Andreas

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