How to add a text into a Rectangle in Matplotlib?

To add text into a rectangle in Matplotlib, you can use the annotate() method to place text at the center point of the rectangle. This technique is useful for creating labeled diagrams, flowcharts, or annotated visualizations.

Steps

• Create a figure using figure() method

• Add a subplot to the current figure

• Create a rectangle using patches.Rectangle() class

• Add the rectangle patch to the plot

• Calculate the center coordinates of the rectangle

• Use annotate() method to place text at the center

• Set axis limits and display the plot

Example

Here's how to create a rectangle with centered text ?

from matplotlib import pyplot as plt, patches

plt.rcParams["figure.figsize"] = [7.00, 3.50]
plt.rcParams["figure.autolayout"] = True

fig = plt.figure()
ax = fig.add_subplot(111)

# Create a rectangle
rectangle = patches.Rectangle((0, 0), 3, 3, edgecolor='orange',
                            facecolor="green", linewidth=7)
ax.add_patch(rectangle)

# Calculate center coordinates
rx, ry = rectangle.get_xy()
cx = rx + rectangle.get_width()/2.0
cy = ry + rectangle.get_height()/2.0

# Add text at the center
ax.annotate("Rectangle", (cx, cy), color='black', weight='bold', 
           fontsize=10, ha='center', va='center')

plt.xlim([-5, 5])
plt.ylim([-5, 5])
plt.show()

Output

The code creates a green rectangle with orange border and "Rectangle" text centered inside it.

Multiple Rectangles with Text

You can also create multiple rectangles with different text labels ?

from matplotlib import pyplot as plt, patches

fig, ax = plt.subplots(figsize=(8, 6))

# Rectangle data: (x, y, width, height, text, color)
rectangles = [
    (1, 1, 2, 1.5, "Box 1", "lightblue"),
    (4, 2, 2.5, 1, "Box 2", "lightgreen"),
    (2, 4, 3, 1.2, "Box 3", "lightcoral")
]

for x, y, width, height, text, color in rectangles:
    # Create rectangle
    rect = patches.Rectangle((x, y), width, height, 
                           edgecolor='black', facecolor=color, linewidth=2)
    ax.add_patch(rect)
    
    # Calculate center and add text
    cx = x + width/2.0
    cy = y + height/2.0
    ax.annotate(text, (cx, cy), ha='center', va='center', 
               fontsize=12, weight='bold')

ax.set_xlim(0, 8)
ax.set_ylim(0, 6)
ax.set_aspect('equal')
plt.title("Multiple Rectangles with Text")
plt.show()

Key Parameters

Conclusion

Use annotate() with calculated center coordinates to add text inside rectangles. The ha='center' and va='center' parameters ensure perfect text alignment within the rectangle bounds.