Pandas DataFrame – Sort by Index

Pandas DataFrame – Sort by Index

To sort a Pandas DataFrame by index, you can use DataFrame.sort_index() method.

To specify whether the method has to sort the DataFrame in ascending or descending order of index, you can set the named boolean argument ascending to True or False respectively.

When the index is sorted, respective rows are rearranged.

Examples

1. Sort DataFrame by index in ascending order

In this example, we shall create a dataframe with some rows and index with an array of numbers. We shall sort the rows of this dataframe, so that the index shall be in ascending order.

To sort the index in ascending order, we call sort_index() method with the argument ascending=True as shown in the following Python program. Or you may ignore the ascending parameter, since the default value for argument ascending is True.

import pandas as pd

# Create a dataframe
df_1 = pd.DataFrame(
    [['Arjun', 70, 86],
     ['Kiku', 80, 76],
	 ['Mama', 99, 99],
     ['Lini', 79, 92]],
    index = [2, 1, 6, 5],
    columns=['name', 'aptitude', 'cooking'])

print(df_1)

# Sort dataframe by index in ascending order
df_1 = df_1.sort_index(ascending=True)

print('\nDataFrame after sorting by index\n')
print(df_1)

Output

Run the above program. We have printed the original DataFrame to the console, followed by sorted DataFrame.

    name  aptitude  cooking
2  Arjun        70       86
1   Kiku        80       76
6   Mama        99       99
5   Lini        79       92

DataFrame after sorting by index

    name  aptitude  cooking
1   Kiku        80       76
2  Arjun        70       86
5   Lini        79       92
6   Mama        99       99

2. Sort DataFrame by index in descending order

In this example, we shall sort the DataFrame based on the descending order of index. For that, we shall pass ascending=False to the sort_index() method.

import pandas as pd

# Create a dataframe
df_1 = pd.DataFrame(
    [['Arjun', 70, 86],
     ['Kiku', 80, 76],
	 ['Mama', 99, 99],
     ['Lini', 79, 92]],
    index = [2, 1, 6, 5],
    columns=['name', 'aptitude', 'cooking'])

print(df_1)

# Sort dataframe by index in descending order
df_1 = df_1.sort_index(ascending=False)

print('\nDataFrame after sorting by index\n')
print(df_1)

Output

Run the program. The sorted dataframe has index [6 5 5 1] in descending order.

    name  aptitude  cooking
2  Arjun        70       86
1   Kiku        80       76
6   Mama        99       99
5   Lini        79       92

DataFrame after sorting by index

    name  aptitude  cooking
6   Mama        99       99
5   Lini        79       92
2  Arjun        70       86
1   Kiku        80       76

Summary

In this tutorial of Python Examples, we learned how to sort a Pandas DataFrame by index in ascending and descending orders.