Pandas DataFrame by Example: GroupBy Examples

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For Dataframe usage examples not related to GroupBy, see Pandas Dataframe by Example

Concatenate strings in a group

This is called GROUP_CONCAT in databases such as MySQL

In the original dataframe, each row is a tag assignment:

user_id content_id tag
1 1 'cool'
2 1 'nice'
1 2 'clever'
3 2 'clever'
3 2 'not bad'
tag_assignments_df.groupby("content_id")['tag'].apply(lambda tags: ','.join(tags))

After the operation, we have one row per content_id and all tags are joined with ','.

content_id tag
1 'cool','nice'
2 'clever','clever','not bad'

Number of of unique column values per group

How many unique users have tagged each movie?



Dialogue & Discussion