无法在 Python 中更改全局变量的值 [重复]

Question

我有一个函数，我想计算它被调用的次数（并以该计数器值作为名称保存图像）。我创建了一个名为 counter 的全局函数。但如果我这样做counter = counter+1。它说Unresolved reference。我错过了什么吗？

代码如下：

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

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

Answer 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)