head() and tail() in Data Analysis Python - Step-by-Step Execution

Concept Flow - head() and tail()

Start with DataFrame

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Call head(n)

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Select first n rows

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Return subset DataFrame

The flow shows how calling head(n) or tail(n) on a DataFrame returns the first or last n rows respectively.

Execution Sample

Data Analysis Python

import pandas as pd

df = pd.DataFrame({'A': range(1,6), 'B': list('abcde')})
print(df.head(3))
print(df.tail(2))

This code creates a DataFrame and shows the first 3 rows with head(3) and last 2 rows with tail(2).

Execution Table

Step	Action	Input DataFrame	Method Called	Parameter n	Output DataFrame
1	Create DataFrame	{'A':[1,2,3,4,5], 'B':['a','b','c','d','e']}	None	None	Full DataFrame with 5 rows
2	Call head(3)	Full DataFrame	head	3	First 3 rows: rows 0,1,2
3	Call tail(2)	Full DataFrame	tail	2	Last 2 rows: rows 3,4
4	End	N/A	N/A	N/A	Execution complete

💡 All requested rows returned; no more steps.

Variable Tracker

Variable	Start	After head(3)	After tail(2)	Final
df	N/A	Full DataFrame with 5 rows	Full DataFrame with 5 rows	Full DataFrame with 5 rows
head_df	N/A	DataFrame with rows 0,1,2	DataFrame with rows 0,1,2	DataFrame with rows 0,1,2
tail_df	N/A	N/A	DataFrame with rows 3,4	DataFrame with rows 3,4

Key Moments - 2 Insights

Why does head(3) return rows 0,1,2 and not 1,2,3?

Because DataFrame rows are zero-indexed, so the first row is index 0. head(3) returns the first three rows starting at index 0, as shown in execution_table step 2.

What happens if n is larger than the number of rows in the DataFrame?

head() or tail() will return all rows without error. This is because they select up to n rows but do not fail if n exceeds the DataFrame size.

Visual Quiz - 3 Questions

Look at the execution_table at step 2, what rows does head(3) return?

A Rows 1,2,3

B Rows 2,3,4

C Rows 0,1,2

D Rows 3,4,5

💡 Hint

Check the Output DataFrame column in step 2 of execution_table.

At which step does tail(2) return the last two rows?

A Step 3

B Step 2

C Step 1

D Step 4

💡 Hint

Look for the method called 'tail' in execution_table.

If we call head(10) on this DataFrame, what will happen?

A Return first 10 rows, error if less than 10

B Return all rows since DataFrame has only 5 rows

C Return empty DataFrame

D Return last 10 rows

💡 Hint

Refer to key_moments about behavior when n exceeds DataFrame size.

Concept Snapshot

head(n) returns the first n rows of a DataFrame.
tail(n) returns the last n rows.
If n > number of rows, all rows are returned.
Rows are zero-indexed.
Useful for quick data preview.

Full Transcript

This lesson shows how to use head() and tail() methods on a DataFrame to view the first or last few rows. The flow starts with a DataFrame, then calls head(n) or tail(n) to select rows. The execution table traces creating a DataFrame with 5 rows, then calling head(3) which returns rows 0,1,2, and tail(2) which returns rows 3,4. Variables track the DataFrame and subsets. Key moments clarify zero-based indexing and behavior when n exceeds row count. The quiz tests understanding of which rows are returned and method behavior. The snapshot summarizes usage and rules for head() and tail().