Cannot change the value of global variable in Python

Question

I have a function that I want to count how many times it is called (and save a image with that counter value as its name). I made a global function called counter . But if I do counter = counter+1. It says Unresolved reference. Am I missing something ?

Here is the code :

import numpy as np
import cv2
counter = 0
def saveImage(img):
    counter = counter+1

    imgs = str(counter) + '.jpg'
    cv2.imwrite('images/'+imgs, img)

add `global counter` inside your function before assigning value to it . — Vikas Periyadath, Aug 06 '18 at 05:36
[use of global keyword](https://stackoverflow.com/questions/4693120/use-of-global-keyword-in-python) — Patrick Artner, Aug 06 '18 at 05:37

score 1 · Accepted Answer · answered Aug 06 '18 at 05:38

1

import numpy as np
import cv2
counter = 0
def saveImage(img):
    global counter  # to modify global variable, you need to explicitly declare so... 
    counter = counter+1

    imgs = str(counter) + '.jpg'
    cv2.imwrite('images/'+imgs, img)

answered Aug 06 '18 at 05:38

hyloop

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Cannot change the value of global variable in Python

1 Answers1