Named colors and hex codes in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to set the line color to a named color 'red' in matplotlib.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [4, 5, 6], color='[1]')
plt.show()

Drag options to blanks, or click blank then click option'

Acyan

Bred

C#00FF00

Dblue

Attempts:

3 left

💡 Hint

Common Mistakes

Using a hex code instead of a named color when the instruction asks for a named color.

Forgetting to put the color name inside quotes.

The color parameter accepts named colors like 'red'. Here, 'red' sets the line color to red.

2fill in blank

medium

Complete the code to set the marker color using a hex code for green.

Matplotlib

import matplotlib.pyplot as plt
plt.scatter([1, 2, 3], [4, 5, 6], marker='o', color='[1]')
plt.show()

Drag options to blanks, or click blank then click option'

Ared

Byellow

Cblue

D#00FF00

Attempts:

3 left

💡 Hint

Common Mistakes

Using a named color instead of a hex code when the instruction asks for a hex code.

Missing the '#' symbol in the hex code.

The hex code '#00FF00' represents green color. Using it sets the marker color to green.

3fill in blank

hard

Fix the error in the code by choosing the correct color format for a blue line.

Matplotlib

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], [3, 2, 1], color=[1])
plt.show()

Drag options to blanks, or click blank then click option'

Ablue

B'blue'

C'#0000FF'

D#0000FF

Attempts:

3 left

💡 Hint

Common Mistakes

Passing color without quotes causing a syntax error.

Using named color without quotes.

The color value must be a string. '#0000FF' is the hex code for blue, so it must be inside quotes.

4fill in blank

hard

Fill both blanks to create a dictionary mapping color names to their hex codes.

Matplotlib

colors = {'red': '[1]', 'green': '[2]'}

Drag options to blanks, or click blank then click option'

A#FF0000

B#00FF00

Cred

Dgreen

Attempts:

3 left

💡 Hint

Common Mistakes

Using color names instead of hex codes in the dictionary values.

Forgetting quotes around hex codes.

Hex codes for red and green are '#FF0000' and '#00FF00' respectively. They must be strings.

5fill in blank

hard

Fill all three blanks to create a dictionary comprehension that maps color names to their uppercase hex codes if the hex code starts with '#'.

Matplotlib

colors = {'red': '#ff0000', 'blue': '#0000ff', 'green': '00ff00'}
result = {k: v[1]() for k, v in colors.items() if v[2]('#')}
print(result)  # Output: [3]

Drag options to blanks, or click blank then click option'

A.upper

B[0]

C{'red': '#FF0000', 'blue': '#0000FF'}

Dstartswith

Attempts:

3 left

💡 Hint

Common Mistakes

Using indexing [0] instead of startswith to check the first character.

Not calling the upper method with parentheses.

Including colors without '#' in the output.

The comprehension converts hex codes to uppercase using .upper() if the string startswith '#'. The output dictionary includes only those keys.

Practice

1. Which of the following is a valid named color in matplotlib?

easy

A. #12345G

B. bluish

C. red

D. 123456

Solution

1. Step 1: Understand named colors in matplotlib

   Matplotlib supports standard color names like 'red', 'blue', 'green', etc.

2. Step 2: Check each option

   red is 'red', a valid named color. #12345G has an invalid hex code with 'G'. bluish 'bluish' is not a recognized name. 123456 is just digits, not a named color.

3. Final Answer:

   red -> Option C

4. Quick Check:

   Named color 'red' is valid [OK]

Hint: Named colors are simple words like 'red' or 'blue' [OK]

Common Mistakes:

• Confusing invalid hex codes as named colors
• Assuming any color-like word is valid
• Using numbers without '#' as colors

2. Which of the following is the correct way to specify a hex color code in matplotlib?

easy

A. "#1a2b3c"

B. "1a2b3c"

C. "#12345"

D. "#xyz123"

Solution

1. Step 1: Recall hex color code format

   Hex codes start with '#' followed by exactly 6 hexadecimal digits (0-9, a-f).

2. Step 2: Validate each option

   "#1a2b3c" has '#' and 6 valid hex digits. "1a2b3c" misses '#'. "#12345" has only 5 digits. "#xyz123" contains invalid letters 'x' and 'z'.

3. Final Answer:

   "#1a2b3c" -> Option A

4. Quick Check:

   Hex code must start with '#' and have 6 hex digits [OK]

Hint: Hex codes start with '#' and have 6 hex digits [OK]

Common Mistakes:

• Omitting the '#' symbol
• Using wrong number of digits
• Including invalid characters

3. What color will the following matplotlib code produce?

import matplotlib.pyplot as plt
plt.plot([1, 2, 3], color="#00FF00")
plt.show()

medium

A. Black

B. Blue

C. Red

D. Green

Solution

1. Step 1: Understand the hex code used

   "#00FF00" is a hex code where red=00, green=FF, blue=00, meaning full green.

2. Step 2: Match hex code to color

   Since green is max and others zero, the line color will be bright green.

3. Final Answer:

   Green -> Option D

4. Quick Check:

   "#00FF00" means green color [OK]

Hint: Hex #00FF00 means full green, no red or blue [OK]

Common Mistakes:

• Confusing hex digits order
• Assuming #00FF00 is blue
• Ignoring case sensitivity in hex

4. Identify the error in this matplotlib color specification:

plt.plot([1, 2, 3], color="#123ABZ")

medium

A. Missing '#' in hex code

B. Invalid hex code due to 'Z'

C. Color name not recognized

D. Syntax error in plot function

Solution

1. Step 1: Check hex code characters

   Hex codes only allow digits 0-9 and letters A-F (case insensitive). 'Z' is invalid.

2. Step 2: Confirm error type

   The code has '#' and correct length, but 'Z' makes it invalid hex code.

3. Final Answer:

   Invalid hex code due to 'Z' -> Option B

4. Quick Check:

   Hex digits must be 0-9 or A-F only [OK]

Hint: Hex codes only use digits 0-9 and letters A-F [OK]

Common Mistakes:

• Ignoring invalid characters in hex
• Confusing missing '#' with invalid chars
• Assuming any letter is allowed in hex

5. You want to plot two lines in matplotlib: one red and one with a custom color #FF8800. Which code snippet correctly sets these colors?

hard

A. plt.plot(x, y1, color='red')
plt.plot(x, y2, color='#FF8800')

B. plt.plot(x, y1, color='#red')
plt.plot(x, y2, color='FF8800')

C. plt.plot(x, y1, color='ff8800')
plt.plot(x, y2, color='red')

D. plt.plot(x, y1, color='red')
plt.plot(x, y2, color='FF8800')

Solution

1. Step 1: Check named color usage

   Named colors like 'red' are used as strings without '#'. Adding '#' to named colors makes them invalid.

2. Step 2: Check hex code usage

   Hex codes must start with '#'. Omitting '#' for hex colors like 'FF8800' or using lowercase without '#' is invalid.

3. Final Answer:

   plt.plot(x, y1, color='red') plt.plot(x, y2, color='#FF8800') -> Option A

4. Quick Check:

   Named colors no '#', hex codes start with '#' [OK]

Hint: Named colors no '#'; hex codes start with '#' [OK]

Common Mistakes:

• Adding '#' to named colors
• Omitting '#' in hex codes
• Using lowercase hex without '#'