Text placement with ax.text in Matplotlib - Interactive Code Practice

Practice - 5 Tasks

1fill in blank

easy

Complete the code to add text at position (2, 3) on the plot.

Matplotlib

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.plot([1, 2, 3], [1, 4, 9])
ax.text(2, 3, [1])
plt.show()

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

A"Hello"

BHello

C2, 3

Dax.plot

Attempts:

3 left

💡 Hint

Common Mistakes

Forgetting to put the text inside quotes.

Passing numbers instead of a string as the text.

The ax.text function requires the text to be a string, so it must be in quotes.

2fill in blank

medium

Complete the code to place the text 'Peak' at the highest point on the plot.

Matplotlib

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
x = [1, 2, 3]
y = [1, 4, 9]
ax.plot(x, y)
ax.text(x[[1]], y[[1]], "Peak")
plt.show()

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

A0

B3

C1

D2

Attempts:

3 left

💡 Hint

Common Mistakes

Using index 3 which is out of range.

Using index 1 which is not the highest point.

The highest point is at index 2 (the third element) in the lists x and y.

3fill in blank

hard

Fix the error in the code to correctly place the text 'Center' at (0.5, 0.5).

Matplotlib

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.text([1], 0.5, 'Center')
plt.show()

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

A'0.5'

Bcenter

C0.5

D0,5

Attempts:

3 left

💡 Hint

Common Mistakes

Using a string instead of a number for the coordinate.

Using a comma instead of a dot for decimal.

The x coordinate must be a number, not a string or invalid syntax.

4fill in blank

hard

Fill both blanks to add text 'Max' at the maximum y value and align it to the right.

Matplotlib

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
x = [1, 2, 3, 4]
y = [2, 5, 1, 7]
ax.plot(x, y)
max_index = y.index(max(y))
ax.text(x[[1]], y[[2]], 'Max', ha='right')
plt.show()

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

Amax_index

B0

D3

Attempts:

3 left

💡 Hint

Common Mistakes

Using different indexes for x and y coordinates.

Using a fixed number instead of max_index.

Both blanks should use max_index to get the x and y coordinates of the max point.

5fill in blank

hard

Fill all three blanks to create a dictionary with words as keys and their lengths as values, but only for words longer than 3 letters.

Matplotlib

words = ['cat', 'elephant', 'dog', 'horse']
lengths = { [1]: [2] for [1] in words if len([3]) > 3 }

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

Aword

Blen(word)

Dwords

Attempts:

3 left

💡 Hint

Common Mistakes

Using 'words' instead of 'word' in the comprehension.

Not using len(word) for the value.

Using different variable names inconsistently.

The dictionary comprehension uses 'word' as key, 'len(word)' as value, and filters words with length > 3.

Practice

1. What does the ax.text function do in matplotlib?

easy

A. It draws a line between two points.

B. It places text at specified x and y coordinates on the plot.

C. It creates a new figure window.

D. It changes the background color of the plot.

Solution

1. Step 1: Understand the purpose of ax.text

   The ax.text function is used to add text labels at specific positions on a plot using x and y coordinates.

2. Step 2: Compare with other options

   Other options describe different matplotlib functions: creating figures, drawing lines, or changing background color, which are not what ax.text does.

3. Final Answer:

   It places text at specified x and y coordinates on the plot. -> Option B

4. Quick Check:

   ax.text adds text labels = C [OK]

Hint: ax.text adds text at (x, y) on the plot [OK]

Common Mistakes:

• Confusing ax.text with plot or figure functions
• Thinking ax.text changes plot colors
• Assuming ax.text draws shapes

2. Which of the following is the correct syntax to place the text 'Hello' at coordinates (2, 3) using ax.text?

easy

A. ax.text(2, 3, 'Hello')

B. ax.text('Hello', 2, 3)

C. ax.text(x=3, y=2, text='Hello')

D. ax.text(3, 2, 'Hello')

Solution

1. Step 1: Recall ax.text parameter order

   The correct order is ax.text(x, y, text), so x=2, y=3, text='Hello' means ax.text(2, 3, 'Hello').

2. Step 2: Check other options

   ax.text('Hello', 2, 3) swaps text and coordinates, ax.text(x=3, y=2, text='Hello') uses wrong parameter names, ax.text(3, 2, 'Hello') swaps x and y values.

3. Final Answer:

   ax.text(2, 3, 'Hello') -> Option A

4. Quick Check:

   ax.text(x, y, text) = A [OK]

Hint: Remember ax.text(x, y, text) order [OK]

Common Mistakes:

• Swapping x and y coordinates
• Putting text before coordinates
• Using wrong parameter names

3. What will the following code display on the plot?

import matplotlib.pyplot as plt
fig, ax = plt.subplots()
ax.plot([1, 2, 3], [4, 5, 6])
ax.text(2, 5, 'Center', fontsize=12, color='red')
plt.show()

medium

A. An error because color must be uppercase.

B. A blue text 'Center' at point (2, 5) on the plot.

C. No text will appear because fontsize is missing.

D. A red text 'Center' at point (2, 5) on the plot.

Solution

1. Step 1: Analyze ax.text parameters

   The code places text 'Center' at (2, 5) with font size 12 and color red, which is valid syntax.

2. Step 2: Understand matplotlib behavior

   Text appears on the plot at the given coordinates with specified style. Color names are case-insensitive, so 'red' works fine.

3. Final Answer:

   A red text 'Center' at point (2, 5) on the plot. -> Option D

4. Quick Check:

   ax.text with color='red' shows red text = A [OK]

Hint: Color names in ax.text are case-insensitive [OK]

Common Mistakes:

• Thinking fontsize is mandatory to show text
• Assuming color must be uppercase
• Expecting text at wrong coordinates

4. Identify the error in this code snippet:

fig, ax = plt.subplots()
ax.text(1, 2, fontsize='large')
plt.show()

medium

A. plt.show() must come before ax.text.

B. ax.text requires x and y as strings, not numbers.

C. The text argument is missing.

D. fontsize must be an integer or float, not a string like 'large'.

Solution

1. Step 1: Check ax.text parameters

   Matplotlib's ax.text requires three positional arguments: x, y, and text (s). The code provides only x=1, y=2, then a keyword argument, missing the text.

2. Step 2: Verify other options

   Numbers for x/y are correct, fontsize='large' is valid, and plt.show() order is fine.

3. Final Answer:

   The text argument is missing. -> Option C

4. Quick Check:

   ax.text requires x, y, text = C [OK]

Hint: ax.text requires x, y, text positional args [OK]

Common Mistakes:

• Omitting the text argument
• Confusing parameter order
• Calling plt.show() too early

5. You want to add a label 'Max Point' exactly above the highest point in this plot:

import matplotlib.pyplot as plt
x = [1, 2, 3, 4]
y = [2, 5, 1, 7]
fig, ax = plt.subplots()
ax.plot(x, y, marker='o')
# Add text here
plt.show()

Which code correctly places the label 0.3 units above the highest point?

hard

A. ax.text(4, 7.3, 'Max Point', va='bottom', ha='center')

B. ax.text(4, 7.3, 'Max Point', ha='center')

C. ax.text(4, 7, 'Max Point', va='top')

D. ax.text(4, 7, 'Max Point', ha='left')

Solution

1. Step 1: Identify highest point coordinates

   The highest y value is 7 at x=4.

2. Step 2: Place text 0.3 units above with correct alignment

   To place text above, y=7.3 is correct. Use vertical alignment va='bottom' so text bottom aligns at 7.3, placing text above the point. Horizontal alignment ha='center' centers text horizontally at x=4.

3. Final Answer:

   ax.text(4, 7.3, 'Max Point', va='bottom', ha='center') -> Option A

4. Quick Check:

   Text above point uses y+offset and va='bottom' = B [OK]

Hint: Use va='bottom' to place text above y coordinate [OK]

Common Mistakes:

• Using va='top' places text below the coordinate
• Not adding offset to y coordinate
• Misaligning text horizontally