[FIXED] How to add a data to the plot in matplotlib?

Issue

How can I have the line plot, with the data coming one by one? I have the code

import matplotlib.pyplot as plt

plt.ion()
plt.plot(1, 2)
plt.pause(2.5)
plt.plot(2, 5)
plt.pause(2.5)

but it does not show the line, if I add 'o' option in plot function or change the plot function to scatter function, it works fine, But I want a line with no markers, how can I do this?

Solution

To respond to the comment about "deleting the current plot", and to improve upon Stefano's answer a bit, we can use Matplotlib's object-oriented interface to do this:

import matplotlib.pyplot as plt

x = [0, 1, 2, 3, 4, 5, 6]
y = [3, 1, 4, 1, 5, 9, 2]

fig, ax = plt.subplots()
ax.set(xlim=(min(x), max(x)), ylim=(min(y), max(y)))

plt.ion()

(line,) = ax.plot([], [])  # initially an empty line

timestep = 0.5  # in seconds

for i in range(1, len(x) + 1):
    line.set_data(x[:i], y[:i])
    plt.pause(timestep)
plt.show(block=True)

This version uses a single Line2D object and modifies its underlying data via set_data. Since Matplotlib doesn't have to draw multiple objects, just the one line, it should scale better once your data becomes large.

Answered By - Dominik Stańczak