Q.Plot a pie to display the radius of the planets and also give an appropriate title to the plot.
[Context: The referenced textbook DataFrame (Program 4-16) is df = pd.DataFrame({'mass': [0.330, 4.87, 5.97], 'radius': [2439.7, 6051.8, 6378.1]}, index=['Mercury', 'Venus', 'Earth']).]

Shape: Code task — write a matplotlib pie chart from a given pandas DataFrame.

The question asks for a pie chart of the radius column. A pie chart displays proportions; each planet's slice will be sized according to its radius value relative to the total.

import pandas as pd
import matplotlib.pyplot as plt

df = pd.DataFrame({'mass': [0.330, 4.87, 5.97], 
                   'radius': [2439.7, 6051.8, 6378.1]}, 
                  index=['Mercury', 'Venus', 'Earth'])

plt.pie(df['radius'], labels=df.index, autopct='%1.1f%%')
plt.title('Radius of Planets')
plt.show()

Key lines:

• plt.pie(df['radius'], labels=df.index, autopct='%1.1f%%') — the first argument is the data (the radius column); labels=df.index uses the planet names ('Mercury', 'Venus', 'Earth') as slice labels; autopct='%1.1f%%' displays each slice's percentage with one decimal place.
• plt.title('Radius of Planets') — sets the chart title as requested.

Expected output:

A pie chart with three slices. Mercury occupies roughly 16.4 % (radius 2439.7), Venus 40.6 % (6051.8), and Earth 42.9 % (6378.1). Each slice is labeled with the planet name and its percentage. The title "Radius of Planets" appears above the chart. …

Why a pie chart is the wrong tool here

A pie chart divides a circle into slices whose areas represent proportions of a total. It answers "what fraction of the whole does each category represent?" For example, if you had the market share of three companies (30%, 50%, 20%), a pie chart makes sense because those percentages sum to 100%.

Planetary radii are absolute measurements in kilometers. Mercury's radius of 2439.7 km is not "a fraction of the total radius of all planets"—that total is a meaningless sum. The radius of Earth is not "37% of something"; it is simply 6378.1 km. Plotting these values as a pie chart forces the viewer to interpret slices as proportions when no such proportion exists in the data.

The textbook question likely intends to teach the syntax of pie charts in pandas/matplotlib, even though the semantic choice is flawed. We will produce the requested pie chart, then show the correct visualization.

The requested (incorrect) pie chart

import pandas as pd
import matplotlib.pyplot as plt

# Given DataFrame
df = pd.DataFrame({
    'mass': [0.330, 4.87, 5.97],
    'radius': [2439.7, 6051.8, 6378.1]
}, index=['Mercury', 'Venus', 'Earth'])

# Plot pie chart of radius
df['radius'].plot(kind='pie', autopct='%1.1f%%', startangle=90, figsize=(6, 6))
plt.title('Radius of Planets (Inappropriate Pie Chart)')
plt.ylabel('')  # Remove the default 'radius' label on the y-axis
plt.show()

What this produces:

• A pie chart with three slices labeled Mercury, Venus, and Earth.
• Each slice shows a percentage: Mercury ≈16.4%, Venus ≈40.7%, Earth ≈42.9% (these are the radii divided by their sum, 14869.6 km).
• The percentages are meaningless—they do not represent any real-world proportion.
• Title: "Radius of Planets (Inappropriate Pie Chart)".

Key lines explained:

• df['radius'].plot(kind='pie', ...) — pandas' .plot() method with kind='pie' creates a pie chart from the Series. Each index label (planet name) becomes a slice.
• autopct='%1.1f%%' — formats the percentage labels to one decimal place.
• startangle=90 — rotates the chart so the first slice starts at the top (12 o'clock position), a common convention.
• plt.ylabel('') — the default pie chart adds a y-axis label equal to the column name ('radius'); we remove it for clarity.

The correct visualization: a bar chart

# Correct plot: bar chart
df['radius'].plot(kind='bar', color='steelblue', edgecolor='black')
plt.title('Radius of Planets')
plt.xlabel('Planet')
plt.ylabel('Radius (km)')
plt.xticks(rotation=0)
plt.grid(axis='y', linestyle='--', alpha=0.6)
plt.tight_layout()
plt.show()

What this produces: …