Pandas check if two columns can be considered the composite key of the dataframe

Question

A sample dataframe:

data = {
    "col_A": ["a","a","b","c"],
    "col_B": [1, 2, 2, 3],
    "col_C": ["demo", "demo", "demo", "demo"]
}

df = pd.DataFrame(data)

Dataframe

col_A   col_B   col_C
a       1       demo
a       2       demo
b       2       demo
c       3       demo

I can easily check if all values in col_A are unique or not by df['col_A'].is_unique.
Is there any way to check for two columns i.e. something like df['col_A', 'col_B'].is_unique

If col_A and col_B are the composite key of the data frame or not?

Asked By: Shaida Muhammad

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Source

Answer 1

You can set all columns that should be included in the composite key as index and then check for is_unique on the index.

df.set_index(['col_A', 'col_B']).index.is_unique

#True

Answered By: Rabinzel

Answer 2

Use DataFrame.duplicated with Series.any()

not df[['col_A', 'col_B']].duplicated().any()

Answered By: ansev

Pandas check if two columns can be considered the composite key of the dataframe

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