Python 3.X - StringVar 总是空的！印刷 ''答案

【问题标题】：Python 3.X - StringVar always empty! Prints ''Python 3.X - StringVar 总是空的！印刷 ''
【发布时间】：2015-11-09 14:55:07
【问题描述】：

from tkinter import *

def Game(result):
    InputScreen = Tk()
    InputScreen.configure(background = "light blue")
    InputScreen.geometry("800x400+100+50")
    InputScreen.title("Input Screen")

    gold_e = StringVar()

    textentry2 = Entry(InputScreen,
                textvariable = gold_e, width = 5).place(x = 325, y = 80)


    button3 = Button(InputScreen,
                     command = lambda: (Update(gold_e)),
                     text = "Update",
                     fg = "black",
                     bg = "red").place(x = 300, y = 300)

    def Update(values):
        print("qqw"+str(values.get())+"wer")
        gold_v = values.get()
        print(gold_v)

        Label19 = Label(InputScreen, text = gold_v,
                        fg = "black",
                        bg = "light blue").place(x = 390,y = 80)

Game(0)

这段代码工作得很好：但是当它被以下代码包围时，它总是返回''（空白），我不知道为什么。

import sys
from tkinter import *

def Game(result):
    InputScreen = Tk()
    InputScreen.configure(background = "light blue")
    InputScreen.geometry("800x400+100+50")
    InputScreen.title("Input Screen")

    goldpps = "0.5"
    silverpps = "0.8"
    copperpps = "1.2"
    oilpps = "3.4"
    wheatpps = "0.6"
    dieselpps = "0.8"
    cocopps = "3.0"

    Label0 = Label(InputScreen, text = "£" + str(result),
                   fg = "black",
                   bg = "light blue").place(x = 100,y = 20)

    Label1 = Label(InputScreen, text = "Commodities",
                   fg = "black",
                   bg = "light blue").place(x = 100,y = 50)

    Label2 = Label(InputScreen, text = "Gold",
                   fg = "black",
                   bg = "light blue").place(x = 125,y = 80)

    Label3 = Label(InputScreen, text = "Silver",
                       fg = "black",
                       bg = "light blue").place(x = 124,y = 110)

    Label4 = Label(InputScreen, text = "Copper",
                   fg = "black",
                   bg = "light blue").place(x = 119,y = 140)

    Label5 = Label(InputScreen, text = "Oil",
                   fg = "black",
                   bg = "light blue").place(x = 130,y = 170)

    Label6 = Label(InputScreen, text = "Wheat",
                   fg = "black",
                   bg = "light blue").place(x = 120,y = 200)

    Label7 = Label(InputScreen, text = "Diesel",
                   fg = "black",
                   bg = "light blue").place(x = 121,y = 230)

    Label8 = Label(InputScreen, text = "Coco",
                   fg = "black",
                   bg = "light blue").place(x = 122,y = 260)

    Label9 = Label(InputScreen, text = "Price per Share",
                   fg = "black",
                   bg = "light blue").place(x = 200,y = 50)

    Label10 = Label(InputScreen, text = "Quantity",
                   fg = "black",
                   bg = "light blue").place(x = 315,y = 50)

    Label11 = Label(InputScreen, text = "Cost",
                   fg = "black",
                   bg = "light blue").place(x = 390,y = 50)

    Label12 = Label(InputScreen, text = goldpps,
                   fg = "black",
                   bg = "light blue").place(x = 227,y = 80)

    Label13 = Label(InputScreen, text = silverpps,
                   fg = "black",
                   bg = "light blue").place(x = 227,y = 110)

    Label14 = Label(InputScreen, text = copperpps,
                   fg = "black",
                   bg = "light blue").place(x = 227,y = 140)

    Label15 = Label(InputScreen, text = oilpps,
                   fg = "black",
                   bg = "light blue").place(x = 227,y = 170)

    Label16 = Label(InputScreen, text = wheatpps,
                   fg = "black",
                   bg = "light blue").place(x = 227,y = 200)

    Label17 = Label(InputScreen, text = dieselpps,
                   fg = "black",
                   bg = "light blue").place(x = 227,y = 230)

    Label18 = Label(InputScreen, text = cocopps,
                   fg = "black",
                   bg = "light blue").place(x = 227,y = 260)


    silver_e = IntVar()
    copper_e = IntVar()
    oil_e = IntVar()
    wheat_e = IntVar()
    diesel_e = IntVar()
    coco_e = IntVar()
    gold_e = StringVar()

    textentry2 = Entry(InputScreen,
                textvariable = gold_e, width = 5).place(x = 325, y = 80)

    textentry3 = Entry(InputScreen,
                textvariable = silver_e, width = 5).place(x = 325, y = 110)

    textentry4 = Entry(InputScreen,
               textvariable = copper_e, width = 5).place(x = 325, y = 140)

    textentry5 = Entry(InputScreen,
               textvariable = oil_e, width = 5).place(x = 325, y = 170)

    textentry6 = Entry(InputScreen,
               textvariable = wheat_e, width = 5).place(x = 325, y = 200)

    textentry7 = Entry(InputScreen,
               textvariable = diesel_e, width = 5).place(x = 325, y = 230)

    textentry8 = Entry(InputScreen,
               textvariable = coco_e, width = 5).place(x = 325, y = 260)

    button3 = Button(InputScreen,
                     command = lambda: (Update(gold_e)),
                     text = "Update",
                     fg = "black",
                     bg = "red").place(x = 300, y = 300)


    def Update(values):
        print("qqw"+str(values.get())+"wer")
        gold_v = values.get()

        print(gold_v)

        Label19 = Label(InputScreen, text = gold_v,
                        fg = "black",
                        bg = "light blue").place(x = 390,y = 80)
        print(values.get())

我花了 5 个多小时让我和一个朋友检查这个，但没有发现错误：如果你说用类重写这个，那不是一个选择。代码的想法是避免编写我们自己的类。

代码本身可以正常工作（在主代码块的底部添加 Game(0)），直到您从另一个文件调用此文件，并将“值”传递给游戏函数。

【问题讨论】：

根本没有return 语句——你为什么希望你的代码返回任何东西？也许您的意思是print 而不是return？如果是，请编辑您的问题。
是的，你说得对，对不起：我刚刚提到代码认为字符串 var 为空（文本条目）
我尝试运行您的第二个代码并在您的行 def Game(result) 上获得了 SyntaxError。这是您正在运行的确切代码吗？请确保此处的代码演示了您遇到的问题。
好的，我做了更正 - 我复制了错误的代码...
谢谢，它现在可以运行了。当我执行它时，程序立即结束，不做任何事情。但这也是您的第一个代码所做的。这是预期的行为吗？

标签： python tkinter tk

【解决方案1】：

我的猜测是您正在创建多个根窗口，因为您说您正在从另一个文件传递“值”，而这个“值”是 tkinter 变量的一个实例。由于您不能在不创建根窗口的情况下创建这些变量之一，因此这个其他文件必须正在创建一个根窗口。

你的整个 tkinter 程序应该只创建一个根窗口。如果您需要创建多个窗口，则需要创建Toplevel 的实例。

【讨论】：