How to check whether the value of a variable is updated or not in Python

Question

I am new to the python and here I have a quick question.

say in a while loop, I have a variable called center, and center is a list, as shown above:

     M = cv2.moments(c)
    center = (int(M["m10"] / M["m00"]), int(M["m01"] / M["m00"]))

center will always be [x,y] and since M is dynamically changed all the time, so does the center.

My question is how can I know whether center is updated or not? If it is updated, how can I mathematically compare this the new center with the previous center?

Thanks.

Your best bet is to keep the previous value in a different variable. — Selcuk
– Selcuk, Commented May 3, 2018 at 3:32
Why not just have a list recording the history of center and append to it every time it is updated? — Primusa
– Primusa, Commented May 3, 2018 at 3:37

Martin Evans · Accepted Answer · 2018-05-03 09:23:19Z

2

You need to keep track of center. To do this create a variable to hold the previous value. This can be initialised to None at the start as you don't have a previous value. For example:

previous_center = None

while True:    

    #
    # Your loop code
    #

    M = cv2.moments(c)
    center = (int(M["m10"] / M["m00"]), int(M["m01"] / M["m00"]))

    if center != previous_center:
        print("New center", center)
        previous_center = center

answered May 3, 2018 at 9:23

Martin Evans

46.9k17 gold badges88 silver badges104 bronze badges

Sign up to request clarification or add additional context in comments.

Collectives™ on Stack Overflow

How to check whether the value of a variable is updated or not in Python

1 Answer 1

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

1 Answer 1

Comments

Your Answer

Sign up or log in

Post as a guest

Related