CODEWITHSUNDEEP
pythonpython-3.xpandas
chippycentra
chippycentra

Reputation: 879

Subset dataframe and groupby pandas

everyone, I have a data frame such as : 

groups  name
1   A
1   B
1   C
1   D
2   E
3   F
3   G
4   H
5   I

and from that I would like to only keep in the data frame the values that are alone in a group:

groups  name
2   E
4   H
5   I

E,H and I are alone in their respective groups.

I tried: 

df[df.groupby(['groups']).count() == 1 ]

But it does not seem to be the solution.

Upvotes: 0

Views: 57

Answers (2)

jezrael
jezrael

Reputation: 863166

Use GroupBy.transform for Series with same size like original DataFrame:

df[df.groupby(['groups'])['name'].transform('size') == 1 ]

Upvotes: 1

cs95
cs95

Reputation: 402814

Use duplicated:

df[~df.groups.duplicated(keep=False)]

   groups name
4       2    E
7       4    H
8       5    I

Or, drop_duplicates.

df.drop_duplicates('groups', keep=False)

   groups name
4       2    E
7       4    H
8       5    I

Upvotes: 2

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