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This tutorial explains how to use pandas.DataFrame.sort_index()the sort method to sort a Pandas DataFrame based on its index.

We will use the DataFrame shown in the above example to explain how to sort a Pandas DataFrame based on the index values.

import pandas as pd

pets_df = pd.DataFrame(
    {
        "Pet": ["Dog", "Cat", "Rabbit", "Fish"],
        "Name": ["Rocky", "Luna", "Coco", "Finley"],
        "Age(Years)": [3, 5, 5, 4],
    },
    index=["4", "2", "1", "3"],
)

print(pets_df)

Output:

      Pet    Name  Age(Years)
4     Dog   Rocky           3
2     Cat    Luna           5
1  Rabbit    Coco           5
3    Fish  Finley           4

pandas.DataFrame.sort_index()method

grammar

DataFrame.sort_index(
    axis=0,
    level=None,
    ascending=True,
    inplace=False,
    kind="quicksort",
    na_position="last",
    sort_remaining=True,
    by=None,
)

parameter

return

Return a DataFrame sorted by index along the specified axis if inplaceTrue True, otherwise None.

By default, we set axis=0, which means the DataFrame will be sorted along the row axis or by index values. If we set axis=1, the columns of the DataFrame will be sorted. By default, this method will sort the DataFrame in ascending order. If you want to sort the DataFrame in descending order, we set ascending=False.

Example: sort_index()Sort a Pandas DataFrame by Index using the

import pandas as pd

pets_df = pd.DataFrame(
    {
        "Pet": ["Dog", "Cat", "Rabbit", "Fish"],
        "Name": ["Rocky", "Luna", "Coco", "Finley"],
        "Age(Years)": [3, 5, 5, 4],
    },
    index=["4", "2", "1", "3"],
)

sorted_df = pets_df.sort_index()

print("Initial DataFrame:")
print(pets_df, "\n")

print("DataFrame Sorted by Index Values:")
print(sorted_df)

Output:

Initial DataFrame:
      Pet    Name Age(Years)
4     Dog   Rocky           3
2     Cat    Luna           5
1 Rabbit    Coco           5
3    Fish Finley           4

DataFrame Sorted by Index Values:
      Pet    Name Age(Years)
1 Rabbit    Coco           5
2     Cat    Luna           5
3    Fish Finley           4
4     Dog   Rocky           3

It sorts the DataFrame in ascending order based on the index values pet_df. To sort the DataFrame based on the index values, we need to specify indexthe parameter. By default, axisthe value of is 0, which sorts the rows of the DataFrame, i.e., it sorts the DataFrame based on the index values.

To sort the DataFrame in descending order based on the index values, we sort_index()set the method ascending=False.

import pandas as pd

pets_df = pd.DataFrame(
    {
        "Pet": ["Dog", "Cat", "Rabbit", "Fish"],
        "Name": ["Rocky", "Luna", "Coco", "Finley"],
        "Age(Years)": [3, 5, 5, 4],
    },
    index=["4", "2", "1", "3"],
)

sorted_df = pets_df.sort_index(ascending=False)

print("Initial DataFrame:")
print(pets_df, "\n")

print("DataFrame Sorted in Descending order based Index Values:")
print(sorted_df)

Output:

Initial DataFrame:
      Pet    Name Age(Years)
4     Dog   Rocky           3
2     Cat    Luna           5
1 Rabbit    Coco           5
3    Fish Finley           4

DataFrame Sorted in Descending order based Index Values:
      Pet    Name Age(Years)
4     Dog   Rocky           3
3    Fish Finley           4
2     Cat    Luna           5
1 Rabbit    Coco           5

pets_dfIt sorts the DataFrame in descending order based on the index values .

Example: sort_index()Sort columns of a Pandas DataFrame using the

To sort the columns of a Pandas DataFrame, we sort_index()set the sorting method axis=1.

import pandas as pd

pets_df = pd.DataFrame(
    {
        "Pet": ["Dog", "Cat", "Rabbit", "Fish"],
        "Name": ["Rocky", "Luna", "Coco", "Finley"],
        "Age(Years)": [3, 5, 5, 4],
    },
    index=["4", "2", "1", "3"],
)

sorted_df = pets_df.sort_index(axis=1)

print("Initial DataFrame:")
print(pets_df, "\n")

print("DataFrame with sorted Columns:")
print(sorted_df)

Output:

Initial DataFrame:
      Pet    Name  Age(Years)
4     Dog   Rocky           3
2     Cat    Luna           5
1  Rabbit    Coco           5
3    Fish  Finley           4

DataFrame with sorted Columns:
   Age(Years)    Name     Pet
4           3   Rocky     Dog
2           5    Luna     Cat
1           5    Coco  Rabbit
3           4  Finley    Fish

It pets_dfsorts the columns of the DataFrame in ascending order by column name.