DataFrame structure (index, columns, values) in Data Analysis Python - Practice Problems & Coding Challenges

Challenge - 5 Problems

❓ query_result

intermediate

What is the output of this DataFrame index query?

Given the DataFrame df below, what will df.index return?

Data Analysis Python

import pandas as pd

df = pd.DataFrame({
    'Name': ['Alice', 'Bob', 'Charlie'],
    'Age': [25, 30, 35]
})

result = df.index

A None

B Index(['Alice', 'Bob', 'Charlie'], dtype='object')

C Index(['Name', 'Age'], dtype='object')

D RangeIndex(start=0, stop=3, step=1)

💡 Hint

The index represents the row labels, which by default are numbers starting at zero.

By default, pandas assigns a RangeIndex starting at 0 for rows if no index is specified.

❓ query_result

intermediate

What does df.columns return for this DataFrame?

Given the DataFrame df below, what will df.columns output?

Data Analysis Python

import pandas as pd

df = pd.DataFrame({
    'City': ['Paris', 'London', 'Berlin'],
    'Population': [2148000, 8982000, 3769000]
})

result = df.columns

A ['Paris', 'London', 'Berlin']

B Index(['City', 'Population'], dtype='object')

C RangeIndex(start=0, stop=3, step=1)

D ['City', 'Population', 'Country']

💡 Hint

Columns represent the names of the data fields in the DataFrame.

The columns attribute returns the labels of the columns as an Index object.

❓ query_result

advanced

What is the output of df.values for this DataFrame?

Given the DataFrame df below, what will df.values return?

Data Analysis Python

import pandas as pd

df = pd.DataFrame({
    'Product': ['Pen', 'Pencil'],
    'Price': [1.5, 0.5]
})

result = df.values

A

[['Pen' 1.5]
 ['Pencil' 0.5]]

B

[['Product' 'Price']
 ['Pen' 1.5]
 ['Pencil' 0.5]]

C [['Pen', 1.5], ['Pencil', 0.5]]

D Index(['Pen', 'Pencil'], dtype='object')

💡 Hint

Values returns the data as a 2D array without the index or columns labels.

df.values returns the underlying data as a numpy array of lists representing rows.

🧠 Conceptual

advanced

Which statement about DataFrame structure is true?

Select the correct statement about the structure of a pandas DataFrame.

A The index labels the rows, and columns label the columns.

B Columns are always numeric and index is always string.

C Values include the index and columns labels.

D The index labels the columns, and columns label the rows.

💡 Hint

Think about what index and columns represent in a table.

The index labels the rows, and columns label the columns. Values are the data inside.

🔧 Debug

expert

Why does this code raise an error when accessing DataFrame values?

Consider this code snippet:

import pandas as pd

df = pd.DataFrame({'A': [1, 2], 'B': [3, 4]})

result = df.values[0]['A']

Why does this raise an error?

A Because df.values returns a numpy array, which does not support string indexing.

B Because df.values returns a dictionary, and dictionaries cannot be indexed by integers.

C Because the DataFrame has no column named 'A'.

D Because the DataFrame is empty.

💡 Hint

Check the type of object returned by df.values and how it can be indexed.

df.values returns a numpy array of the data, so indexing by string like ['A'] is invalid.