Rcparams for global defaults in Matplotlib - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is rcParams in matplotlib?

rcParams is a dictionary-like object in matplotlib that stores default settings for plots, such as colors, fonts, and line styles. Changing rcParams changes the look of all plots globally.

beginner

How do you change the default figure size globally using rcParams?

You set matplotlib.rcParams['figure.figsize'] = (width, height) where width and height are in inches. This changes the size for all future plots.

intermediate

What file can you edit to permanently change matplotlib's global defaults?

You can edit the matplotlibrc file. This file contains default settings that matplotlib reads every time it starts, so changes here apply globally and persistently.

intermediate

How do you reset rcParams to matplotlib's default settings in your code?

Use matplotlib.rcdefaults() to reset all rcParams to their original default values during runtime.

beginner

Give an example of changing the default font size globally using rcParams.

Set matplotlib.rcParams['font.size'] = 14 to make all plot text use font size 14 by default.

What does matplotlib.rcParams control?

A Only figure size of plots

B Global default plot settings

C Only colors of plots

D Only font styles

rcParams controls many global default settings including colors, sizes, fonts, and more.

How do you change the default line width globally in matplotlib?

A matplotlib.rcParams['line.width'] = 2

B matplotlib.rcParams['lines.width'] = 2

C matplotlib.rcParams['linewidth'] = 2

D matplotlib.rcParams['lines.linewidth'] = 2

The correct key is lines.linewidth to set default line width.

Which function resets rcParams to default values during a session?

A matplotlib.rcdefaults()

B matplotlib.clear()

C matplotlib.reset_rcParams()

D matplotlib.reset()

matplotlib.rcdefaults() resets all rcParams to default values.

Where do you put permanent changes to matplotlib defaults?

A In the matplotlibrc file

B In your Python script

C In the plot title

D In the plot legend

The matplotlibrc file stores permanent global default settings.

What type of object is rcParams?

A Tuple

B List

C Dictionary-like

D Set

rcParams behaves like a dictionary with keys and values.

Explain how to change the global default figure size in matplotlib using rcParams.

Think about setting a key in rcParams to a size tuple.

Describe the purpose of the matplotlibrc file and how it relates to rcParams.

Consider how to make changes that last beyond a single script.

Practice

1. What is the main purpose of rcParams in matplotlib?

easy

A. To set global style defaults for all plots

B. To create new plots with random styles

C. To save plots as image files

D. To import data into matplotlib

Solution

1. Step 1: Understand what rcParams controls

   rcParams is a dictionary-like object in matplotlib that stores default settings for plot styles.

2. Step 2: Identify the purpose of setting rcParams

   Setting rcParams changes the default appearance of all plots globally, so you don't have to style each plot individually.

3. Final Answer:

   To set global style defaults for all plots -> Option A

4. Quick Check:

   rcParams = global style defaults [OK]

Hint: Remember rcParams sets defaults for all plots globally [OK]

Common Mistakes:

• Thinking rcParams creates plots
• Confusing rcParams with saving files
• Believing rcParams imports data

2. Which of the following is the correct way to change the default figure size using rcParams?

easy

A. plt.rcParams['figure.size'] = (8, 6)

B. plt.rcParams['figsize'] = (8, 6)

C. plt.rcParams['fig.size'] = (8, 6)

D. plt.rcParams['figure.figsize'] = (8, 6)

Solution

1. Step 1: Recall the exact rcParams key for figure size

   The correct key is 'figure.figsize', which expects a tuple for width and height.

2. Step 2: Check the syntax for assignment

   Assigning a tuple like (8, 6) to plt.rcParams['figure.figsize'] sets the default figure size.

3. Final Answer:

   plt.rcParams['figure.figsize'] = (8, 6) -> Option D

4. Quick Check:

   Key 'figure.figsize' = correct syntax [OK]

Hint: Use 'figure.figsize' key exactly for figure size [OK]

Common Mistakes:

• Using wrong key names like 'figsize' or 'figure.size'
• Assigning a list instead of a tuple
• Forgetting to import matplotlib.pyplot as plt

3. What will be the default line width for all plots after running this code?

import matplotlib.pyplot as plt
plt.rcParams['lines.linewidth'] = 3
print(plt.rcParams['lines.linewidth'])

medium

A. 1

B. 2

C. 3

D. Error

Solution

1. Step 1: Understand the code effect on rcParams

   The code sets 'lines.linewidth' to 3, changing the default line width globally.

2. Step 2: Check the printed value

   After setting, printing plt.rcParams['lines.linewidth'] outputs 3, confirming the change.

3. Final Answer:

   3 -> Option C

4. Quick Check:

   Set then print 'lines.linewidth' = 3 [OK]

Hint: Setting rcParams key changes default; print confirms value [OK]

Common Mistakes:

• Expecting default 1 without setting
• Confusing linewidth with linestyle
• Thinking print causes error

4. Identify the error in this code that tries to set the default font size:

import matplotlib.pyplot as plt
plt.rcParams['font.size'] = 'large'

medium

A. The key 'font.size' is incorrect

B. The value should be a number, not a string

C. plt.rcParams cannot be modified

D. Missing import statement

Solution

1. Step 1: Check the key correctness

   'font.size' is the correct rcParams key for font size.

2. Step 2: Validate the value type

   The value must be a number (int or float), not a string like 'large'.

3. Final Answer:

   The value should be a number, not a string -> Option B

4. Quick Check:

   font.size value must be numeric [OK]

Hint: Font size values must be numbers, not words [OK]

Common Mistakes:

• Using string values for numeric rcParams keys
• Assuming rcParams keys are case-insensitive
• Forgetting to import matplotlib.pyplot

5. You want all your matplotlib plots to have a dark background and white grid lines by default. Which rcParams settings should you apply?

hard

A. plt.rcParams['axes.facecolor'] = 'black'; plt.rcParams['grid.color'] = 'white'

B. plt.rcParams['figure.facecolor'] = 'white'; plt.rcParams['grid.color'] = 'black'

C. plt.rcParams['axes.facecolor'] = 'white'; plt.rcParams['grid.color'] = 'black'

D. plt.rcParams['figure.facecolor'] = 'black'; plt.rcParams['grid.color'] = 'black'

Solution

1. Step 1: Identify the rcParams key for plot background

   'axes.facecolor' sets the background color inside the plot area, so set it to 'black' for dark background.

2. Step 2: Identify the rcParams key for grid line color

   'grid.color' controls the color of grid lines; setting it to 'white' makes them visible on a dark background.

3. Final Answer:

   plt.rcParams['axes.facecolor'] = 'black'; plt.rcParams['grid.color'] = 'white' -> Option A

4. Quick Check:

   Dark background + white grid = axes.facecolor black, grid.color white [OK]

Hint: Use axes.facecolor for background, grid.color for grid lines [OK]

Common Mistakes:

• Changing figure.facecolor instead of axes.facecolor
• Setting grid color to black on black background
• Confusing axes and figure color keys