Why my code just writes the last variable?

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The code below should make 10 videos with names 1,2,3,..., 10 but it just writes the last video and other videos are 0 kb. I am not sure where is the problem. The code is reproducible.


import matplotlib.pyplot as plt
import matplotlib
import numpy as np
from cv2 import VideoWriter, VideoWriter_fourcc

pixels = 600
my_dpi = 100
num_geo=10
FPS=1
seconds = 100

load_x = np.random.rand(14,100,3)
coord = np.random.rand(5,2,10)


for i in range(num_geo):
    fourcc = VideoWriter_fourcc(*'MP42')
    video = VideoWriter((str(i) + ".mp4"), fourcc, FPS, (pixels, pixels))
    
for j in range(100):
    fig = plt.figure(num_geo,figsize=( pixels/my_dpi,  pixels/my_dpi),facecolor='k', dpi=my_dpi)  
    plt.axes([0,0,1,1])
    rectangle = plt.Rectangle((-300, -300), 600, 600, fc='k')
    plt.gca().add_patch(rectangle)
    a=load_x[0,j,:].tolist()
    a=matplotlib.colors.to_hex(a)

    plt.plot([coord[0][0][i], coord[4][0][i]], [coord[0][1][i], coord[4][1][i]], color=str(a), lw=8, antialiased=True)
    plt.axis('off')
    plt.axis([-300,300,-300,300])
        
    fig.canvas.draw()
    
    data = np.frombuffer(fig.canvas.tostring_rgb(), dtype=np.uint8)
    data = data.reshape(fig.canvas.get_width_height()[::-1] + (3,))   
 
    video.write(data)
video.release()
matplotlib video opencv for-loop python
1 Answers

Indent the second loop and all subsequent lines.

EDIT: you should probably pull a bunch of unnecessary calculations outside the second for loop as well. See updated version below:

for i in range(num_geo):
    fourcc = VideoWriter_fourcc(*'MP42')
    video = VideoWriter((str(i) + ".mp4"), fourcc, FPS, (pixels, pixels))
    fig = plt.figure(num_geo,figsize=( pixels/my_dpi, pixels/my_dpi),facecolor='k', dpi=my_dpi)  
    plt.axes([0,0,1,1])
    for j in range(100):
        rectangle = plt.Rectangle((-300, -300), 600, 600, fc='k')
        plt.gca().add_patch(rectangle)
        a=load_x[0,j,:].tolist()
    a=matplotlib.colors.to_hex(a)

    plt.plot([coord[0][0][i], coord[4][0][i]], [coord[0][1][i], coord[4][1][i]], color=str(a), lw=8, antialiased=True)
    plt.axis('off')
    plt.axis([-300,300,-300,300])
            
    fig.canvas.draw()
        
    data = np.frombuffer(fig.canvas.tostring_rgb(), dtype=np.uint8)
        data = data.reshape(fig.canvas.get_width_height()[::-1] + (3,))   
    
    video.write(data)
    video.release()
user_37916400
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