为什么.get（）不会迭代并在Tkinter中工作？

Question

我为我的网络类制作了这个客户端，它应该连接到我们教授设置的MUD服务器，但是我在Tkinter的条目小部件中遇到问题，当按下“Enter”按钮时，条目小部件中的文本是应该从submit_value()函数打印到shell，但我得到一个错误，说当从它调用.get()时，条目小部件不存在，任何人都可以帮我弄清楚这个错误吗？

from tkinter import *
from sys import exit

def button_func():
        print("Test")

def submit_value():
        print("Entered Value: %s" % (userEntry.get()))

class TestClient(Frame):
    def __init__(self, master):
        Frame.__init__(self, master)
        self.pack()

        for n in range(3):
            self.grid_rowconfigure(n, weight=1)

        for n in range(8):
            self.grid_columnconfigure(n, weight=1)

        lb1 = Listbox(self, width=20,height=24)
        lb1.insert(1,"WoW")
        lb1.grid(row=0, column=0, columnspan=2, sticky='news')

        t1 = Text(self, width=60)
        t1.grid(row=0, column=3, columnspan=3)

        lb2 = Listbox(self, width=20,height=24)
        lb2.insert(1,"Hi")
        lb2.grid(row=0, column=6, columnspan=2, sticky='news')

        la1 = Label(self, text="Value entry:")
        la1.grid(row=1, column=0)

        userEntry = StringVar()
        e1 = Entry(self, width=40, textvariable=userEntry)
        e1.grid(row=1, column=1, columnspan=6)

        e2 = Button(self, text="Enter", command=submit_value)
        e2.grid(row=1, column=5, columnspan=10)


        b1 = Button(self, text="Start", width=10,padx=10,pady=10, command=button_func)
        b1.grid(row=2, column=0)

        b2 = Button(self, text="Change Room", width=10,padx=10,pady=10, command=button_func)
        b2.grid(row=2, column=3)

        b3 = Button(self, text="FIGHT", width=10,padx=10,pady=10, command=button_func)
        b3.grid(row=2, column=4)

        b4 = Button(self, text="PvP FIGHT", width=10,padx=10,pady=10, command=button_func)
        b4.grid(row=2, column=5)

        b5 = Button(self, text="Loot", width=10,padx=10,pady=10, command=button_func)
        b5.grid(row=2, column=6)

        b6 = Button(self, text="Leave", width=10,padx=10,pady=10, command=button_func)
        b6.grid(row=2, column=7)

        stats = Listbox(self, width= 20)
        stats.insert(1,"health:")
        stats.grid(row=3, column=0, columnspan=8, sticky='news')

root = Tk()
root.title = "Test program"
tw = TestClient(root)
root.mainloop()

Answer 1

userEntry是TestClient.__init__的局部变量。它不能在函数范围之外使用。你可以通过使用全局变量解决这个问题：

from tkinter import *
from sys import exit

userEntry = object

def button_func():
    print("Test")

def submit_value():
    global userEntry
    print("Entered Value: %s" % (userEntry.get()))

class TestClient(Frame):
    def __init__(self, master):
        global userEntry
        Frame.__init__(self, master)
        self.pack()

        for n in range(3):
            self.grid_rowconfigure(n, weight=1)

        for n in range(8):
            self.grid_columnconfigure(n, weight=1)

        lb1 = Listbox(self, width=20,height=24)
        lb1.insert(1,"WoW")
        lb1.grid(row=0, column=0, columnspan=2, sticky='news')

        t1 = Text(self, width=60)
        t1.grid(row=0, column=3, columnspan=3)

        lb2 = Listbox(self, width=20,height=24)
        lb2.insert(1,"Hi")
        lb2.grid(row=0, column=6, columnspan=2, sticky='news')

        la1 = Label(self, text="Value entry:")
        la1.grid(row=1, column=0)

        userEntry = StringVar()
        e1 = Entry(self, width=40, textvariable=userEntry)
        e1.grid(row=1, column=1, columnspan=6)

        e2 = Button(self, text="Enter", command=submit_value)
        e2.grid(row=1, column=5, columnspan=10)


        b1 = Button(self, text="Start", width=10,padx=10,pady=10, command=button_func)
        b1.grid(row=2, column=0)

        b2 = Button(self, text="Change Room", width=10,padx=10,pady=10, command=button_func)
        b2.grid(row=2, column=3)

        b3 = Button(self, text="FIGHT", width=10,padx=10,pady=10, command=button_func)
        b3.grid(row=2, column=4)

        b4 = Button(self, text="PvP FIGHT", width=10,padx=10,pady=10, command=button_func)
        b4.grid(row=2, column=5)

        b5 = Button(self, text="Loot", width=10,padx=10,pady=10, command=button_func)
        b5.grid(row=2, column=6)

        b6 = Button(self, text="Leave", width=10,padx=10,pady=10, command=button_func)
        b6.grid(row=2, column=7)

        stats = Listbox(self, width= 20)
        stats.insert(1,"health:")
        stats.grid(row=3, column=0, columnspan=8, sticky='news')

root = Tk()
root.title = "Test program"
tw = TestClient(root)
root.mainloop()

上面的代码创建了userEntry作为全局变量，因此它可以在整个程序中的任何地方使用。