Update plot in for loop in function - python-3.x

Question

I'm trying to call a function like in the example below, and plot while running the code. The real values that I get as y-data are not really random numbers, but the point is that I would like it to get updated real-time. The plot in my example code below is just empty though and isn't getting updated.
import numpy as np
import matplotlib.pyplot as plt
import random as rnd
import time
initial_time = time.time()
def multiple_runs(number_of_runs):
x_data, y_data = [], []
fig, ax = plt.subplots()
sc = ax.scatter(x_data, y_data)
plt.draw()
for i in range(0, number_of_runs):
x_data.append(i+1)
y_data.append(rnd.randint(0,100))
sc.set_offsets(np.c_[x_data, y_data])
fig.canvas.draw_idle()
plt.pause(0.1)
print ('Total time after run number ' + str(i+1) + ': ' + str(time.time() - initial_time))
multiple_runs(100)
UPDATE:
Thanks #ImportanceOfBeingErnest , I got the code to work. However my problem right now is that the figure closes down as soon as it's finished, is there anyway to keep it open? I tried using plt.waitforbuttonpress() but I get a strange error from QTimer, not sure how or why. This is my working example code;
import numpy as np
import matplotlib.pyplot as plt
import random as rnd
import time
initial_time = time.time()
def multiple_runs(number_of_runs):
x_data, y_data = [], []
x_data2, y_data2 = [], []
fig, ax = plt.subplots(2, sharex = True)
sc = ax[0].scatter(x_data, y_data)
sc2 = ax[1].scatter(x_data2, y_data2)
ax[0].set(xlim=(0,100), ylim=(0,100))
ax[1].set(xlim=(0,100), ylim=(0,100))
plt.draw()
for i in range(0, number_of_runs):
x_data.append(i+1)
y_data.append(rnd.randint(0,100))
x_data2.append(i+1)
y_data2.append(rnd.randint(0,100))
sc.set_offsets(np.c_[x_data, y_data])
sc2.set_offsets(np.c_[x_data2, y_data2])
fig.canvas.draw_idle()
plt.pause(0.1)
print ('Total time after run number ' + str(i+1) + ': ' + str(time.time() - initial_time))
multiple_runs(100)
UPDATE2:
I tried using FuncAnimation, but getting the error TypeError: update() missing 2 required positional arguments: 'y' and 'y2'. I still need to use the for-loop because in my real code I'm using the previous values of y, to calculate the next values of y. This is my example code which is giving me the error;
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation
import random as rnd
import time
initial_time = time.time()
def multiple_runs(number_of_runs):
x_data, y_data = [], []
x_data2, y_data2 = [], []
fig, ax = plt.subplots(2, sharex = True)
sc = ax[0].scatter(x_data, y_data)
sc2 = ax[1].scatter(x_data2, y_data2)
ax[0].set(xlim=(0,100), ylim=(0,100))
ax[1].set(xlim=(0,100), ylim=(0,100))
def update(i, y, y2):
x_data.append(i+1)
y_data.append(y)
x_data2.append(i+1)
y_data2.append(y2)
sc.set_offsets(np.c_[x_data, y_data])
sc2.set_offsets(np.c_[x_data2, y_data2])
print ('Total time after run number ' + str(i+1) + ': ' + str(time.time() - initial_time))
for i in range(0, number_of_runs):
y = rnd.randint(0,100)
y2 = rnd.randint(0,100)
update(i,y,y2)
ani = FuncAnimation(fig, update, frames=number_of_runs, interval=100, repeat=False)
plt.show()
multiple_runs(100)

Answer 1

As commented, I would recommend to use FuncAnimation. This would look as follows in your case. Note that in order to close the window, one would need to press q or close it with the mouse.
import numpy as np
import matplotlib.pyplot as plt
from matplotlib.animation import FuncAnimation
import random as rnd
import time
initial_time = time.time()
def multiple_runs(number_of_runs):
x_data, y_data = [], []
x_data2, y_data2 = [], []
fig, ax = plt.subplots(2, sharex = True)
sc = ax[0].scatter(x_data, y_data)
sc2 = ax[1].scatter(x_data2, y_data2)
ax[0].set(xlim=(0,100), ylim=(0,100))
ax[1].set(xlim=(0,100), ylim=(0,100))
def get_ydata(i):
y = rnd.randint(0,100)
y2 = rnd.randint(0,100)
return y, y2
def update(i):
y, y2 = get_ydata(i)
x_data.append(i+1)
y_data.append(y)
x_data2.append(i+1)
y_data2.append(y2)
sc.set_offsets(np.c_[x_data, y_data])
sc2.set_offsets(np.c_[x_data2, y_data2])
ani = FuncAnimation(fig, update, frames=number_of_runs, interval=100, repeat=False)
plt.show()
multiple_runs(100)