CODEWITHSUNDEEP
pythonpandasdataframe
zodiac645
zodiac645

Reputation: 191

Negate isin - pandas

I have the following line in my code where I group df based on a column Package, and calculate the size of each group based on a criteria on another column Id.

df.groupby("Package")["Id"].apply(lambda x: x.isin(someList).sum())
Package
P1       1
P2       12
P3       52
P4       123
P5       5421
P6       53
P7       64
Name: Id, dtype: int64

My question is that I also need to calculate the size of each group where x is not in someList. How can I do that? Should I just tilde somewhere?

Upvotes: 1

Views: 1476

Answers (1)

jezrael
jezrael

Reputation: 862841

In your solution add ~ with parentheses to lambda function:

df.groupby("Package")["Id"].apply(lambda x: (~x.isin(someList)).sum())

Or use syntactic sugar - create Series of not membership and aggregate by Series df["Package"]:

(~df["Id"].isin(someList)).groupby(df["Package"]).sum()

Similar cleaner idea with column Id filled by mask, so possible aggregate with column name:

df.assign(Id = ~df["Id"].isin(someList)).groupby("Package")["Id"].sum()

Upvotes: 1

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