pandas 1.4.2

ParametersReturns
duplicated(self, keep: "Literal['first', 'last', False]" = 'first') -> 'npt.NDArray[np.bool_]'

Duplicated values are indicated as True values in the resulting array. Either all duplicates, all except the first, or all except the last occurrence of duplicates can be indicated.

Parameters

keep : {'first', 'last', False}, default 'first'

The value or values in a set of duplicates to mark as missing.

Returns

np.ndarray[bool]

Indicate duplicate index values.

See Also

DataFrame.duplicated

Equivalent method on pandas.DataFrame.

Index.drop_duplicates

Remove duplicate values from Index.

Series.duplicated

Equivalent method on pandas.Series.

Examples

By default, for each set of duplicated values, the first occurrence is set to False and all others to True:

This example is valid syntax, but we were not able to check execution
>>> idx = pd.Index(['lama', 'cow', 'lama', 'beetle', 'lama'])
... idx.duplicated() array([False, False, True, False, True])

which is equivalent to

This example is valid syntax, but we were not able to check execution
>>> idx.duplicated(keep='first')
array([False, False,  True, False,  True])

By using 'last', the last occurrence of each set of duplicated values is set on False and all others on True:

This example is valid syntax, but we were not able to check execution
>>> idx.duplicated(keep='last')
array([ True, False,  True, False, False])

By setting keep on False , all duplicates are True:

This example is valid syntax, but we were not able to check execution
>>> idx.duplicated(keep=False)
array([ True, False,  True, False,  True])
See :

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File: /pandas/core/indexes/base.py#2926
type: <class 'function'>
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