How to display a y value on each point in a plot?

Question

I'm drawing this multi graph and would like to show the y value on each point.

import matplotlib.pyplot as plt
import numpy as np

x = np.array([0, 1])
y1 = np.array([float(2.396), float(2.339)])
y2 = np.array([float(1.500), float(1.460)])
y3 = np.array([float(1.067), float(0.933)])
y4 = np.array([float(0.800), float(0.800)])
y5 = np.array([float(0.076), float(0.067)])
y = (float(2.396), float(2.339), float(1.500), float(1.460), float(1.067), float(0.933), float(0.800), float(0.800),
     float(0.076), float(0.067))
my_xticks = ['I1', 'I2']
plt.xticks(x, my_xticks)
plt.plot(x, y1, marker='o', markerfacecolor='blue', markersize=12, color='blue', linewidth=2)
plt.plot(x, y2, marker='o', markerfacecolor='olive', markersize=12, color='olive', linewidth=2)
plt.plot(x, y3, marker='o', markerfacecolor='red', markersize=12, color='red', linewidth=2)
plt.plot(x, y4, marker='o', markerfacecolor='skyblue', markersize=12, color='skyblue', linewidth=2)
plt.plot(x, y5, marker='o', markerfacecolor='green', markersize=12, color='green', linewidth=2)
plt.grid(True, linestyle="--", color='black')
plt.show()

Answer 1

Matplotlib's annotate provides a lot of functionality to add text to a plot, optionally including an arrow. Note that matplotlib doesn't search for an optimal position to place the text, you need to provide x,y position (in the coordinates of the axes of the plot) and an optional offset (in pixel coordinates) to position the text.

An example:

import matplotlib.pyplot as plt
import numpy as np

xs = np.array([0, 1])
y2 = np.array([1.500, 1.460])
y3 = np.array([1.067, 0.933])
y1 = np.array([2.396, 2.339])
y4 = np.array([0.800, 0.800])
y5 = np.array([0.076, 0.067])
plt.xticks(xs, ['I1', 'I2'])
for ys, color in zip([y1, y2, y3, y4, y5], ['blue', 'olive', 'red', 'skyblue', 'green']):
    plt.plot(xs, ys, marker='o', markerfacecolor=color, markersize=5, color=color, linewidth=2)
    for x, y in zip(xs, ys):
        plt.annotate(y,
                     xy=(x, y),
                     xytext=(15 if x == 0 else -15, -20 if y > 2 or y == 0.8 else 10),
                     textcoords='offset points',
                     arrowprops=dict(facecolor='black', arrowstyle='->'),
                     horizontalalignment='left' if x == 0 else 'right',
                     verticalalignment='bottom')
plt.grid(True, linestyle="--", color='black')
plt.show()