matplotlib measure the width of text
import matplotlib.pyplot as plt
# some example plot
plt.plot([1,2,3], [2,3,4])
t = plt.text(1.1, 3.1, "my text", fontsize=18)
# to get the text bounding box
# we need to draw the plot
plt.gcf().canvas.draw()
# get bounding box of the text
# in the units of the data
bbox = t.get_window_extent()
.inverse_transformed(plt.gca().transData)
print(bbox)
# prints: Bbox(x0=1.1, y0=3.0702380952380954, x1=1.5296875, y1=3.2130952380952382)
# plot the bounding box around the text
plt.plot([bbox.x0, bbox.x0, bbox.x1, bbox.x1, bbox.x0],
[bbox.y0, bbox.y1, bbox.y1, bbox.y0, bbox.y0])
plt.show()