Jupyter使用报错TypeError: 'NoneType' object is not subscriptable

原因部分变量为空

可以print看一下变量原因

TypeErrorTraceback (most recent call last)
<ipython-input-3-54e75ded8d30> in <module>
      4 
      5 img = cv2.imread('img.jpg')
----> 6 img2 = img[:,:,::-1]
      7 plt.imshow(img)

TypeError: 'NoneType' object is not subscriptable