set_index(self, keys, drop: 'bool' = True, append: 'bool' = False, inplace: 'bool' = False, verify_integrity: 'bool' = False)

Set the DataFrame index (row labels) using one or more existing columns or arrays (of the correct length). The index can replace the existing index or expand on it.

Parameters

keys : label or array-like or list of labels/arrays

This parameter can be either a single column key, a single array of the same length as the calling DataFrame, or a list containing an arbitrary combination of column keys and arrays. Here, "array" encompasses Series , Index , np.ndarray , and instances of ~collections.abc.Iterator .

drop : bool, default True

Delete columns to be used as the new index.

append : bool, default False

Whether to append columns to existing index.

inplace : bool, default False

If True, modifies the DataFrame in place (do not create a new object).

verify_integrity : bool, default False

Check the new index for duplicates. Otherwise defer the check until necessary. Setting to False will improve the performance of this method.

Returns

DataFrame or None

Changed row labels or None if inplace=True .

Set the DataFrame index using existing columns.

See Also

DataFrame.reindex

Change to new indices or expand indices.

DataFrame.reindex_like

Change to same indices as other DataFrame.

DataFrame.reset_index

Opposite of set_index.

Examples

This example is valid syntax, but we were not able to check execution

>>> df = pd.DataFrame({'month': [1, 4, 7, 10],
...                    'year': [2012, 2014, 2013, 2014],
...                    'sale': [55, 40, 84, 31]})
... df
   month  year  sale
0      1  2012    55
1      4  2014    40
2      7  2013    84
3     10  2014    31

Set the index to become the 'month' column:

This example is valid syntax, but we were not able to check execution

>>> df.set_index('month')
       year  sale
month
1      2012    55
4      2014    40
7      2013    84
10     2014    31

Create a MultiIndex using columns 'year' and 'month':

This example is valid syntax, but we were not able to check execution

>>> df.set_index(['year', 'month'])
            sale
year  month
2012  1     55
2014  4     40
2013  7     84
2014  10    31

Create a MultiIndex using an Index and a column:

This example is valid syntax, but we were not able to check execution

>>> df.set_index([pd.Index([1, 2, 3, 4]), 'year'])
         month  sale
   year
1  2012  1      55
2  2014  4      40
3  2013  7      84
4  2014  10     31

Create a MultiIndex using two Series:

This example is valid syntax, but we were not able to check execution

>>> s = pd.Series([1, 2, 3, 4])
... df.set_index([s, s**2])
      month  year  sale
1 1       1  2012    55
2 4       4  2014    40
3 9       7  2013    84
4 16     10  2014    31

See :

Back References

The following pages refer to to this document either explicitly or contain code examples using this.

pandas.core.generic.NDFrame.reindex pandas.core.frame.DataFrame.reset_index pandas.core.frame.DataFrame.reindex pandas.core.series.Series.reindex pandas.core.generic.NDFrame.reindex_like

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