为什么我的Tk按钮被自动按下？

Question

在下面的代码中，单击按钮应将黑色文本从Hello更改为Goodbye。但是当我运行该程序时，它立即说再见。

from Tkinter import *
from tkMessageBox import *
print "this is a test"


class Demo(Frame):
    def __init__(self):
        self.createGUI()
        print "init"
        #self.__mainWindow = Tk()
    def destroy(self):
        print "destroy"
    def createGUI(self):
        Frame.__init__(self)
        self.pack(expand = YES, fill = BOTH)
        self.master.title("Demo")
        self.trackLabel = StringVar()
        self.trackLabel.set("Hello")
        self.trackDisplay = Label(self, font = "Courier 14", textvariable = self.trackLabel, bg = "black", fg = "green")
        self.trackDisplay.grid(sticky = W+E+N+S)
        self.button1 = Button(self, text = "Click Me", width = 10, command = self.bpress())
        self.button1.grid(row = 2, column = 0, sticky = W+E+N+S)

    def bpress(self):
        self.trackLabel.set("Goodbye")
# run the program
def main():
    tts = Demo()
    tts.mainloop()

if __name__ == "__main__":
    main()

Answer 1

因为您在创建self.bpress按钮时呼叫self.button1：

self.button1 = Button(self, text = "Click Me", width = 10, command = self.bpress())
#                                                                               ^^

只需删除括号并将command指定给self.bpress函数对象本身：

self.button1 = Button(self, text = "Click Me", width = 10, command = self.bpress)

Answer 2

供将来参考：

如果您想将参数发送到该功能，只需添加lambda:

即可

使用命令callback()的按钮示例：

yourButton = Tkinter.Button(root, text="Go!", command= lambda: callback(variableOne, variableTwo, variableThree)).pack()