如何在python中修复NameError

Question

我也尝试将两个窗口分别设置为面板A和PanelB，但出现以下错误

如果PanelA为None或PanelB如果None：NameError：名称'panelA'未定义

from tkinter import *
from PIL import Image, ImageTk
from tkinter import filedialog
import cv2

def select_image():
        global panelA, panelB
        path = filedialog.askopenfilename()
        if len(path) > 0:
                image = cv2.imread(path)
                gray = cv2.cvtColor(image, cv2.COLOR_BGR2GRAY)
                edged = cv2.Canny(gray, 50, 100)
                image = cv2.cvtColor(image, cv2.COLOR_BGR2RGB)
                image = Image.fromarray(image)
                edged = Image.fromarray(edged)
                image = ImageTk.PhotoImage(image)
                edged = ImageTk.PhotoImage(edged)    
        if panelA is None or panelB is None:
                panelA = Label(image=image)
                panelA.image = image
                panelA.pack(side="left", padx=10, pady=10)
                panelB = Label(image=edged)
                panelB.image = edged
                panelB.pack(side="right", padx=10, pady=10)
        else:
                panelA.configure(image=image)
                panelB.configure(image=edged)
                panelA.image = image
                panelB.image = edged
root = Tk()
panelA = None
panelB = None

btn = Button(root, text="Select an image", command=select_image)
btn.pack(side="bottom", fill="both", expand="yes", padx="10", pady="10")

root.mainloop()

Answer 1

您可以定义全局变量，但是如果要在if语句中进行比较，则还需要初始化它们：

global panelA, panelB
panelA, panelB = None, None

Answer 2

请修正您的缩进.panelA，panelB =''