Tk：如果用户输入的不是字符串，如何删除 tk 条目？

Question

我想使用最有效的方法来限制用户只能输入数字。例如：当他们在条目中输入字母时，该确切条目将被清除。有没有什么方法可以做到结构上的变化最少？

这是我的代码：[the ???????标志是我卡住的地方]

import tkinter as tk
from tkinter import ttk

class App:
    """Main class for a simple application"""

def __init__(self, master):
    """Main initialisation for the main app"""
    # create a top frame or window which we can add things to it
    self.topFrame = tk.Frame(master)
    self.topFrame.pack()
    # create a holder (notebook) for tabs
    self.note = ttk.Notebook(self.topFrame)
    # create four different tabs for the main screen
    self.tab1 = ttk.Frame(self.note)
    self.tab2 = ttk.Frame(self.note)
    self.tab3 = ttk.Frame(self.note)
    self.tab4 = ttk.Frame(self.note)
    # add four different tabs for the main screen with various names
    self.note.add(self.tab1, text='   Demography   ')
    self.note.add(self.tab2, text='   Urban Economy   ')
    self.note.add(self.tab3, text='   Land Use   ')
    self.note.add(self.tab4, text='   Urban Transportation   ')
    self.note.pack()
    # add a frame to each tab
    self.demog_frame = tk.Frame(self.tab1)
    self.demog_frame.pack()
    self.eco_frame = tk.Frame(self.tab2)
    self.eco_frame.pack()        
    self.land_frame = tk.Frame(self.tab3)
    self.land_frame.pack()
    self.trans_frame = tk.Frame(self.tab4)
    self.trans_frame.pack()        
    # add label frames to {DEMOGRAPHY TAB}
    self.demog_flable_1 = tk.LabelFrame(self.demog_frame, text='Population Growth:')
    self.demog_flable_1.grid(row=0, column=0, ipadx=0, ipady=10, padx=0)


    # add info to the first LabelFrame
    self.d_p_grwt_label_fy = tk.Label(self.demog_flable_1, text='population of year n |', pady=0, font='Arial 8')
    self.d_p_grwt_label_fy.grid(row=0, column=0)
    self.d_p_grwt_label_sy = tk.Label(self.demog_flable_1, text='population of year n+1 |', font='Arial 8')
    self.d_p_grwt_label_sy.grid(row=0, column=1)
    self.d_p_grwt_label_fyy = tk.Label(self.demog_flable_1, text='year n eg:1999 |', font='Arial 8')
    self.d_p_grwt_label_fyy.grid(row=2, column=0)
    self.d_p_grwt_label_syy = tk.Label(self.demog_flable_1, text='year n+1 eg:2006 |', font='Arial 8')
    self.d_p_grwt_label_syy.grid(row=2, column=1)
    self.d_p_grwt_entry_fy = tk.Entry(self.demog_flable_1, width=12)
    self.d_p_grwt_entry_fy.bind("<KeyRelease>", func=self.popfunc_1)
    self.d_p_grwt_entry_fy.grid(row=1, column=0)
    self.d_p_grwt_entry_sy = tk.Entry(self.demog_flable_1, width=12)
    self.d_p_grwt_entry_sy.grid(row=1, column=1)
    self.d_p_grwt_entry_fyy = tk.Entry(self.demog_flable_1, width=12)
    self.d_p_grwt_entry_fyy.grid(row=3, column=0)
    self.d_p_grwt_entry_syy = tk.Entry(self.demog_flable_1, width=12)
    self.d_p_grwt_entry_syy.grid(row=3, column=1)
    #----------------------------------------------
    self.d_p_grwt_dscrpt_label = tk.Label(self.demog_flable_1, text='population absolute change \u2193', font='Arial 8')
    self.d_p_grwt_dscrpt_label.grid(row =0, column=2)
    self.d_p_grwt_dscrpt_label1 = tk.Label(self.demog_flable_1, text='population annual absolute change \u2193', font='Arial 8')
    self.d_p_grwt_dscrpt_label1.grid(row =2, column=2)
    self.d_p_grwt_dscrpt_label2 = tk.Label(self.demog_flable_1, text='population annual percent change \u2193', font='Arial 8')
    self.d_p_grwt_dscrpt_label2.grid(row =4, column=2)

def popfunc_1(self, *args):
    try:    
        p1 = int(self.d_p_grwt_entry_fy.get())
        p2 = int(self.d_p_grwt_entry_sy.get())
        y1 = int(self.d_p_grwt_entry_fyy.get())
        y2 = int(elf.d_p_grwt_entry_syy.get())

        print(x1)

    except ValueError:
       ???? 





root = tk.Tk()
root.title('Urban Calculator')
root.geometry('420x200')
app = App(root)

root.mainloop()

在课程的底部，我尝试通过ValueError 排除字符串。如果我写一个pass 很好，但我也希望清除该条目。有没有办法指向p1 或p2 并说出导致错误被清除的任何一个？

Answer 1

有没有办法指向 p1 或 p2 并说出导致错误被清除的任何一个？

是的，但不是一次全部。您必须单独对每个条目运行 try/except。

例如，您可以将条目字段加载到列表中，然后使用循环将每个条目绑定到您的方法，然后使用传递的事件与小部件进行交互。

请参阅下面的示例，如果您有任何问题，请告诉我。

import tkinter as tk
from tkinter import ttk


class App(tk.Tk):
    def __init__(self):
        super().__init__()
        self.title('Urban Calculator')
        self.geometry('420x200')
        topFrame = tk.Frame(self)
        topFrame.pack()
        note = ttk.Notebook(topFrame)
        tab1 = ttk.Frame(note)
        note.add(tab1, text='   Demography   ')
        note.pack()
        demog_frame = tk.Frame(tab1)
        demog_frame.pack()
        demog_flable_1 = tk.LabelFrame(demog_frame, text='Population Growth:')
        demog_flable_1.grid(row=0, column=0, ipadx=0, ipady=10, padx=0)
        tk.Label(demog_flable_1, text='population of year n |', pady=0, font='Arial 8').grid(row=0, column=0)
        tk.Label(demog_flable_1, text='population of year n+1 |', font='Arial 8').grid(row=0, column=1)
        tk.Label(demog_flable_1, text='year n eg:1999 |', font='Arial 8').grid(row=2, column=0)
        tk.Label(demog_flable_1, text='year n+1 eg:2006 |', font='Arial 8').grid(row=2, column=1)
        entry_list = [tk.Entry(demog_flable_1, width=12),
                           tk.Entry(demog_flable_1, width=12),
                           tk.Entry(demog_flable_1, width=12),
                           tk.Entry(demog_flable_1, width=12)]
        entry_list[0].grid(row=1, column=0)
        entry_list[1].grid(row=1, column=1)
        entry_list[2].grid(row=3, column=0)
        entry_list[3].grid(row=3, column=1)
        for entry in entry_list:
            entry.bind("<KeyRelease>", func=self.popfunc_1)

        tk.Label(demog_flable_1, text='population absolute change \u2193', font='Arial 8').grid(row=0, column=2)
        tk.Label(demog_flable_1, text='population annual absolute change \u2193',
                 font='Arial 8').grid(row=2, column=2)
        tk.Label(demog_flable_1, text='population annual percent change \u2193',
                 font='Arial 8').grid(row=4, column=2)

    def popfunc_1(self, event):
        x = event.widget.get()
        try:
            entry_value = int(x)
            print(entry_value)
        except ValueError:
            print('error')
            event.widget.delete(len(x) - 1, 'end')


if __name__ == '__main__':
    App().mainloop()