Topic: Python Matplotlib – Important 20 Interview Questions with Answers

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### 1. What is Matplotlib in Python?

Answer:
Matplotlib is a comprehensive library for creating static, animated, and interactive visualizations in Python. It is highly customizable and works well with NumPy and pandas.

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### 2. What is the difference between `plt.plot()` and `plt.scatter()`?

Answer:
• plt.plot() is used for line plots.
• plt.scatter() is used for creating scatter (dot) plots.

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### 3. How do you add a title and axis labels to a plot?

Answer:

plt.title("My Plot")
plt.xlabel("X-axis")
plt.ylabel("Y-axis")

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### 4. How can you create multiple subplots in one figure?

Answer:
Use plt.subplots() to create a grid layout of subplots.

fig, axs = plt.subplots(2, 2)

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### 5. How do you save a plot to a file?

Answer:

plt.savefig("myplot.png", dpi=300)

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### 6. What is the role of `plt.show()`?

Answer:
It displays the figure window containing the plot. Required for interactive sessions or scripts.

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### 7. What is a histogram in Matplotlib?

Answer:
A histogram is used to visualize the frequency distribution of numeric data using plt.hist().

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### 8. What does `plt.figure(figsize=(8,6))` do?

Answer:
It creates a new figure with a specified width and height (in inches).

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### 9. How do you add a legend to your plot?

Answer:

plt.legend()

You must specify label='something' in your plot function.

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### 10. What are some common `cmap` (color map) options?

Answer:
'viridis', 'plasma', 'hot', 'coolwarm', 'gray', 'jet', etc.

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### 11. How do you create a bar chart?

Answer:

plt.bar(categories, values)

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### 12. How can you rotate x-axis tick labels?

Answer:

plt.xticks(rotation=45)

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### 13. How do you add a grid to the plot?

Answer:

plt.grid(True)

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### 14. What is the difference between `imshow()` and `matshow()`?

Answer:
• imshow() is general-purpose for image data.
• matshow() is optimized for 2D matrices and auto-configures the axes.

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### 15. How do you change the style of a plot globally?

Answer:

plt.style.use('ggplot')

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### 16. How can you add annotations to specific data points?

Answer:

plt.annotate('label', xy=(x, y), xytext=(x+1, y+1), arrowprops=dict(arrowstyle='->'))

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### 17. How do you create a pie chart in Matplotlib?

Answer:

plt.pie(data, labels=labels, autopct='%1.1f%%')

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### 18. How do you plot a heatmap in Matplotlib?

Answer:

plt.imshow(matrix, cmap='hot')
plt.colorbar()

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### 19. Can Matplotlib create 3D plots?

Answer:
Yes. Use:

from mpl_toolkits.mplot3d import Axes3D

Then:

fig = plt.figure()
ax = fig.add_subplot(111, projection='3d')

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### 20. How do you add error bars to your data?

Answer:

plt.errorbar(x, y, yerr=errors, fmt='o')

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### Exercise

Choose 5 of the above functions and implement a mini-dashboard with line, bar, and pie plots in one figure layout.

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