Matplotlib set_data使我的程序冻结（请检查“更新后的问题”）

Question

I am trying to plot two updating plots, one is a diagram and the other one is an image captured from the camera.

I get an error on this line:

"current_line.set_data(y_data)" in the "update" function.  
The error says: "AttributeError: 'list' object has no attribute 'set_data'".

Any idea why am I getting this error? If I comment out this line I will get changing images from the camera and everything except the second plot seems fine (because the second plot is not updating) but I need the second plot to be updated as well.

y_data = [0]
# Capture intial frame
ret, initial_frame = lsd.cap.read()

# Function for making the initial figure
def makeFigure():
    fig = plt.figure()

    # Show frame
    ax1 = plt.subplot2grid((2, 2), (0, 0), colspan=2)
    plot_frame = ax1.imshow(initial_frame, animated=True)

    # Set the limits of the plot and plot the graph
    ax2 = plt.subplot2grid((2, 2), (1, 0), colspan=2)
    ax2.set_title('Title')
    ax2.set_ylabel('Y-Label')
    ax2.set_ylim(0, 100)
    ax2.set_xlim(0, 100)
    ax2.grid()
    line = ax2.plot(y_data, 'o-')

    return fig, plot_frame, line

def update(i, current_frame, current_line, y_data):
    # Capture original frame_new_RGB from camera
    ret, frame_new_original = lsd.cap.read()

    # Changing frame_new_original's color order
    frame_new_RGB = cv2.cvtColor(frame_new_original, cv2.COLOR_BGRA2RGB)

    y_data.append(randint(0, 9))

    # Update figure
    current_line.set_data(y_data)

    # Update frame
    current_frame.set_data(frame_new_RGB)


# Make figures and animate the figures
curr_fig, curr_frame, curr_line = makeFigure()
anim = FuncAnimation(curr_fig, update, fargs=[curr_frame, curr_line, y_data], interval=10)

plt.show()

# When everything done, release the capture
lsd.cap.release()
cv2.destroyAllWindows()

UPDATED ISSUE:

The first problem is solved but now I am facing another one. My program freezes after running it and it does not generate any errors.There is another thing that might be relevant to this problem, I am multithreading and this piece of code is in the main thread.

Answer 1

ax.plot returns a list of Line2D instances (in your case, its a 1-item list). This is because it is possible to plot multiple lines in one go with ax.plot .

So, in your case, you just need to grab the first item of the list. The simplest way is probably to change this line:

line = ax2.plot(y_data, 'o-')

to this:

line, = ax2.plot(y_data, 'o-')

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Note that while your question is about setting the data of the line, rather than adding a legend , this Q&A are relevant here, since the solution is the same: Python legend attribute error