DataFrame structure (index, columns, values) in Data Analysis Python - Step-by-Step Execution

Concept Flow - DataFrame structure (index, columns, values)

Create DataFrame

↓

Set Index (row labels)

↓

Set Columns (column labels)

↓

Fill Values (data cells)

↓

DataFrame Ready for Use

This flow shows how a DataFrame is built step-by-step: first created, then rows get labels (index), columns get labels, and finally the data values fill the cells.

Execution Sample

Data Analysis Python

import pandas as pd

data = {'Name': ['Alice', 'Bob'], 'Age': [25, 30]}
df = pd.DataFrame(data)
print(df)

This code creates a DataFrame from a dictionary and prints its structure showing index, columns, and values.

Execution Table

Step	Action	Index	Columns	Values
1	Create DataFrame from dict	[0, 1]	['Name', 'Age']	[['Alice', 25], ['Bob', 30]]
2	Print DataFrame	[0, 1]	['Name', 'Age']	[['Alice', 25], ['Bob', 30]]
3	End	[0, 1]	['Name', 'Age']	[['Alice', 25], ['Bob', 30]]

💡 DataFrame created with default index 0,1; columns 'Name' and 'Age'; values filled from dictionary.

Variable Tracker

Variable	Start	After 1	Final
df.index	None	RangeIndex(start=0, stop=2, step=1)	RangeIndex(start=0, stop=2, step=1)
df.columns	None	Index(['Name', 'Age'], dtype='object')	Index(['Name', 'Age'], dtype='object')
df.values	None	[['Alice' 25] ['Bob' 30]]	[['Alice' 25] ['Bob' 30]]

Key Moments - 2 Insights

Why does the DataFrame have index values 0 and 1?

Because when creating from a dictionary without specifying index, pandas assigns default integer index starting at 0, as shown in execution_table step 1.

Are the columns 'Name' and 'Age' part of the data or labels?

They are column labels, not data values. The values are inside the cells under these columns, as seen in execution_table columns and values.

Visual Quiz - 3 Questions

Look at the execution_table at step 1, what are the column labels of the DataFrame?

A ['Name', 'Age']

B [0, 1]

C ['Alice', 'Bob']

D [25, 30]

💡 Hint

Check the 'Columns' column in execution_table row with Step 1.

At which step does the DataFrame get its values filled?

A Step 3

B Step 2

C Step 1

D Values are never filled

💡 Hint

Look at the 'Values' column in execution_table; values appear at Step 1.

If we specify index=['a', 'b'] when creating the DataFrame, how would df.index change?

A [0, 1]

B ['a', 'b']

C ['Name', 'Age']

D ['Alice', 'Bob']

💡 Hint

Refer to variable_tracker for df.index values and how index labels are assigned.

Concept Snapshot

DataFrame structure:
- Index: row labels (default 0,1,...)
- Columns: column labels (from data keys)
- Values: data cells under columns
Create with pd.DataFrame(data), index optional
Access with df.index, df.columns, df.values

Full Transcript

A DataFrame is like a table with rows and columns. When you create it from a dictionary, pandas sets default row labels called index (0,1,2...) and column labels from the dictionary keys. The data fills the cells under these columns. You can see the index with df.index, columns with df.columns, and the actual data with df.values. This example shows a DataFrame with two rows labeled 0 and 1, columns 'Name' and 'Age', and values for Alice and Bob.