Tkinter中使用Python 3的计算器程序的问题

Question

here is the code (see below for edits):

from tkinter import *

my_int_var = 0

def button_1_method():      #what's important is this method and the button_1 defined below
    my_int_var.set = my_int_var.get + 1
    entry_field.set = my_int_var

root = Tk()
frame_1 = Frame(root)
frame_1.pack()
frame_2 = Frame(root)
frame_2.pack()
frame_3 = Frame(root)
frame_3.pack()
frame_4=Frame(root)
frame_4.pack()

entry_field = Entry(frame_4)
entry_field.pack()

button_add = Button(frame_1, text = "add")
button_subtract = Button(frame_1, text = "subtract")
button_multiply = Button(frame_1, text = "multiply")
button_divide = Button(frame_1, text = "divide")
button_calculate = Button(frame_3, text = "calculate")
button_calculate.pack()

button_add.grid(row = 0)
button_subtract.grid(row = 0, column = 1)
button_multiply.grid(row=0,column= 2)
button_divide.grid(row=0,column = 3)

button_1 = Button(frame_2,text = "1", command = button_1_method())
button_2 = Button(frame_2,text = "2")
button_3 = Button(frame_2,text = "3")
button_4 = Button(frame_2,text = "4")
button_5 = Button(frame_2,text = "5")
button_6 = Button(frame_2,text = "6")
button_7 = Button(frame_2,text = "7")
button_8 = Button(frame_2,text = "8")
button_9 = Button(frame_2,text = "9")
button_0 = Button(frame_2,text = "0")

button_1.grid(row = 0)
button_2.grid(row = 0,column = 1)
button_4.grid(row=0, column= 3)
button_5.grid(row=0, column= 4)
button_6.grid(row=0, column= 5)
button_7.grid(row=0, column= 6)
button_8.grid(row=0, column= 7)
button_9.grid(row=0, column= 8)
button_0.grid(row=0, column= 9)

root.mainloop()

I am trying to add '1' to the number displayed in the entry whenever the 'one' button is pushed. however I am playing around with the button_1_method and getting various errors. How can I fix it so that whenever I press the one button, a '1' is added to the number in the entry (and the same with the rest of the number buttons)?

EDIT: I changed it a little:

my_str_var = StringVar()

def button_1_method(my_str_var):
    my_str_var.set(my_str_var.get() + 1)
    entry_field.set(my_str_var)


button_1 = Button(frame_2,text = "1", command = button_1_method)

now this is the error I'm getting:

Traceback (most recent call last):
  File "C:/Users/TOTTY/PycharmProjects/beginnerpoject/python calculator.py", line 5, in <module>
    my_str_var = StringVar()
  File "C:\Python34\lib\tkinter\__init__.py", line 332, in __init__
    Variable.__init__(self, master, value, name)
  File "C:\Python34\lib\tkinter\__init__.py", line 236, in __init__
    self._root = master._root()
AttributeError: 'NoneType' object has no attribute '_root'

Answer 1

set is a method , which you have to call . And same for get .

So, instead of this:

my_int_var.set = my_int_var.get + 1

Do this:

my_int_var.set(my_int_var.get() + 1)

---

But you've got another problem on top of that. my_int_var isn't a Tk IntVar , it's just a plain old int, which has no such methods. And it's also not attached to your Entry widget in any way.

So, you need to create a Tk var with my_int_var = IntVar() , and then you need to pass it to the widget either in the constructor or in a config call.

If you look at the docs where you found the get and set methods, you'll see some examples that should make it obvious. In particular, see the third example under Patterns in the Entry docs (but make sure to read the whole section).

---

There are other problems beyond the ones directly related to your error. For example:

button_1 = Button(frame_2,text = "1", command = button_1_method())

You want to pass the function, button_1_method as the command. But that's not what you're doing; you're calling that function, getting its return value, and passing that as the command. (It's exactly the opposite of your first problem, where you want to call a function but left the parens off. You can't expect Python to guess when you want to call a function and when you want to use it as a value; the parentheses are how you tell it to call the function.)

Similarly, as I mentioned in a comment, even if you get this all right, adding 1 to a number is not what the 1 key on a calculator does. You need to get the difference between a number and its string representation straight or you're going to have a lot more problems with this app. 1 != '1' , but str(1) == '1' and 1 == int('1')

In your updated version, you've changed it to use a StringVar , whose value is of course a string, and you're trying to add 1 to its value. That's the same problem. Again, the number 1 and the string '1' are not the same thing.

And you're also trying to call a set method on an Entry object when no such method exists. Read the Entry docs to see how to change or replace the value of an Entry —but if you're using a StringVar (as in your edited code), you don't need to do this in the first place. That's the whole point of binding a variable to a widget; changes to either one affect the other. So, when you call my_str_var.get , you're getting the current contents of the Entry widget, and when you call my_str_var.set , you're replacing the contents of the widget.