While循环条目无效的Python

Question

IM试图造成一个循环，迫使用户在输入框中输入一定的数字。如果他们没有输入正确的数字，则循环应重新出现，让他们继续尝试直到用户插入20。当前该框会一遍又一遍地闪烁，如果用户未选择20，则用户将无法再次输入任何内容。第一次。

BankBoxEntry2 = g.Entry(g.Point(200,75), 4)
BankBoxEntry2.draw(win)
win.getMouse()
myText7.setText("")
Bankmessage = int (BankBoxEntry2.getText())

while Bankmessage != 20 :
        scaredBankText =g.Text(g.Point(200,25),'The street game buy in is $20 \n this is not enough money')

        scaredBankText.draw(win)
        BankBoxEntry2.undraw()
        BankBoxEntry2 = g.Entry(g.Point(200,75), 4)
        BankBoxEntry2.draw(win)
        Bankmessage = int (BankBoxEntry2.getText())

if Bankmessage == 20 :
    myBankText =g.Text(g.Point(200,25),'Lets go to the street game!!!')
    myBankText.draw(win)