sort_index() for index sorting in Pandas - Step-by-Step Execution

Concept Flow - sort_index() for index sorting

Start with DataFrame

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Call sort_index()

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Check index order

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If sorted

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Return sorted DataFrame

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End

The DataFrame is passed to sort_index(), which checks the index order and returns a new DataFrame sorted by index.

Execution Sample

Pandas

import pandas as pd

df = pd.DataFrame({'A': [3, 1, 2]}, index=[2, 0, 1])
sorted_df = df.sort_index()

This code creates a DataFrame with an unsorted index and sorts it by index using sort_index().

Execution Table

Step	DataFrame Index Before	Action	DataFrame Index After	Output
1	[2, 0, 1]	Call sort_index()	[0, 1, 2]	{'A': [1, 2, 3]}
2	[0, 1, 2]	Return sorted DataFrame	[0, 1, 2]	{'A': [1, 2, 3]}
3	N/A	End	N/A	Sorted DataFrame returned

💡 sort_index() completes after sorting index from [2, 0, 1] to [0, 1, 2]

Variable Tracker

Variable	Start	After sort_index()	Final
df.index	[2, 0, 1]	[2, 0, 1]	[2, 0, 1] (unchanged)
sorted_df.index	N/A	[0, 1, 2]	[0, 1, 2]

Key Moments - 2 Insights

Does sort_index() change the original DataFrame's index?

No, sort_index() returns a new DataFrame with sorted index; the original DataFrame's index remains unchanged as shown in execution_table row 1 and variable_tracker.

What happens if the index is already sorted?

sort_index() returns a DataFrame identical to the original, as no reordering is needed, shown in execution_table step 2.

Visual Quiz - 3 Questions

Look at the execution_table, what is the index of sorted_df after step 1?

A [2, 0, 1]

B [0, 1, 2]

C [1, 2, 0]

D [3, 1, 2]

💡 Hint

Check the 'DataFrame Index After' column in execution_table row 1.

According to variable_tracker, does df.index change after calling sort_index()?

A No, it stays [2, 0, 1]

B Yes, it changes to [0, 1, 2]

C It becomes empty

D It becomes [1, 0, 2]

💡 Hint

Look at the 'df.index' row in variable_tracker after sort_index() is called.

If the original index was already sorted, what would sort_index() return?

A A DataFrame with reversed index

B An error

C A DataFrame with the same index order

D An empty DataFrame

💡 Hint

Refer to key_moments explanation about sorted index behavior.

Concept Snapshot

sort_index() sorts a DataFrame by its index.
It returns a new DataFrame; original stays unchanged.
Default is ascending order.
Useful to reorder rows by index labels.
Syntax: df.sort_index()
Can sort rows or columns by index.

Full Transcript

This visual execution shows how pandas sort_index() works. We start with a DataFrame with index [2, 0, 1]. When we call sort_index(), pandas checks the index order and returns a new DataFrame sorted by index [0, 1, 2]. The original DataFrame's index remains unchanged. The execution table tracks these steps clearly. Key moments clarify that sort_index() does not modify the original DataFrame but returns a sorted copy. The visual quiz tests understanding of index changes and behavior when the index is already sorted. The concept snapshot summarizes the main points for quick reference.