如何解决清空输入框时的属性错误

Question

我在写代码的时候遇到了这个错误：

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python33\lib\tkinter\__init__.py", line 1482, in __call__
    return self.func(*args)
  File "C:\Users\Bryan\Desktop\Python overhoorprogramma.py", line 18, in verify
    oentry.delete(0,END)
AttributeError: 'NoneType' object has no attribute 'delete'

我已经用过搜索功能，但似乎没有解决我的问题。我想要实现的是清空一个输入框。

# Maak een grafische interface / Create a graphical interface
gui = Tk()
gui.resizable(width=FALSE, height=FALSE)

# Verklaringen / Definitions
def verify():
    overify = antwoord.get()

    if overify == Nederlandsevertaling:
        ctypes.windll.user32.MessageBoxA(0, "Goed gedaan", "werkend", 1)
        oentry.delete(0,END)
    else:
            ctypefs.windll.user32.MessageBoxA(0, "Slecht gedaan", "Werkend", 1)
            oentry.delete()

antwoord = StringVar()
willekeurig = random.randint(0,9)

# Laad de database / Load the database
cnx = mysql.connector.connect(user='-', password='-', host='-', database='Overhoor')
cursor = cnx.cursor()

query = "SELECT FRwoord, NLwoord FROM unite8app1 WHERE id=%s"
cursor.execute(query, (willekeurig,))

for (FRwoord, NLwoord) in cursor:
    Fransevertaling = FRwoord
    Nederlandsevertaling = NLwoord

# Uiterlijk van het venster / Appearance of the window
gui.configure(background="white")
gui.title("Overhoorprogramma - Bryan")

# Grafische objecten / Graphical objects
style = ttk.Style()

olabel = ttk.Label(gui,text=Fransevertaling,font=("Times", 18), background="white").grid(row=0, column=0,padx=5, pady=5, sticky="W")
oentry = ttk.Entry(gui,textvariable=antwoord, font=("Times", 18)).grid(row=1, column=0,padx=5, pady=5)
obutton = ttk.Button(gui,text="Suivant", command = verify).grid(row=1, column=1,padx=5, pady=5)

# Stop de grafische interface
gui.mainloop()

---

oentry = ttk.Entry(gui,textvariable=antwoord, font=("Times", 18)).grid(row=1, column=0,padx=5, pady=5)
obutton = ttk.Button(gui,text="Suivant", command = verify).grid(row=1, column=1,padx=5, pady=5)

如果你按下obutton，应该能清空oentry里的文本。为此我尝试使用：

oentry.delete(0,END)

还有几种不同的.delete方法。但它并没有清空文本框，反而给我返回了一个错误。

Exception in Tkinter callback
Traceback (most recent call last):
  File "C:\Python33\lib\tkinter\__init__.py", line 1482, in __call__
    return self.func(*args)
  File "C:\Users\Bryan\Desktop\Python overhoorprogramma.py", line 18, in verify
    oentry.delete(0,END)
AttributeError: 'NoneType' object has no attribute 'delete'

有没有解决办法？

Answer 1

我之前在实际“创建”文本框之前写了删除和插入的语句，像这样：

my_text.delete(1.0, tk.END)
my_text.insert(tk.INSERT, title)

my_text = tk.Text(frame2, width=40, height=10, font=("Helvetica", 18))
my_text.pack(pady=25, padx=25)

把创建的部分放在前面就解决了这个问题：

my_text = tk.Text(frame2, width=40, height=10, font=("Helvetica", 18))
my_text.pack(pady=25, padx=25)

my_text.delete(1.0, tk.END)
my_text.insert(tk.INSERT, title)

Answer 2

每个Tkinter控件的grid方法都是就地操作的，也就是说它总是返回None。

换句话说，像下面这样的写法：

olabel = ttk.Label(gui,text=Fransevertaling,font=("Times", 18), background="white").grid(row=0, column=0,padx=5, pady=5, sticky="W")

应该改成这样：

olabel = ttk.Label(gui,text=Fransevertaling,font=("Times", 18), background="white")
olabel.grid(row=0, column=0,padx=5, pady=5, sticky="W")

也就是说，grid方法应该单独写在一行。