如何在Python的tkinter中从链接菜单项传递值？

huangapple
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英文:

How to pass values from a linked menu item in python tkinter?

问题

To create a variable to hold and pass the label of the item selected from a drop-down menu in tkinter, you can use the following code:

  1. import tkinter as tk
  3. def selection_changed(event):
  4.     selected_label = selection.get()
  5.     print(f"Selected label: {selected_label}")
  7. root = tk.Tk()
  8. root.geometry("200x170")
  10. selection = tk.StringVar(root)
  11. selection.set("Select an item")  # Set an initial value
  13. options = ["Option 1", "Option 2", "Option 3"]
  14. option_menu = tk.OptionMenu(root, selection, *options)
  15. option_menu.pack()
  17. selection.trace("w", selection_changed)
  19. root.mainloop()

As for sending a second variable into a function in tkinter at the same time, you can modify the selection_changed function to accept both the selected label and your spare variable:

  1. def selection_changed(event):
  2.     selected_label = selection.get()
  3.     spare_variable = "Your spare variable here"  # Replace with your actual spare variable
  4.     print(f"Selected label: {selected_label}")
  5.     print(f"Spare variable: {spare_variable}")

Then, when you call the selection_changed function, you can pass your spare variable along with the selected label.

英文:

How to create a variable to hold and pass label of the item selected from a drop down menu? While I'm here, may I ask how to send a second (spare) variable into a function in tkinter at the same time. I'm not using classes or "OptionMenu".
Here's what I have...

  1. ## In a tkinter I have this...
  3. import tkinter as tk
  4. from tkinter import Toplevel, Button, Tk, Menu, Frame
  6. root = Tk()
  8. xr, yr = 200, 170
  9. rg = str(xr) + "x" + str(yr) # concatinating
  10. root.geometry(rg)
  12. selection = tk.StringVar(root)
  14. print(f"Before option menu selected, selection.get() = {selection.get()}")
  16. def confirm_stage(*args):
  17.     global selection
  18.     print(f"selection.get(): {selection.get()}")
  19.     print(f"selection: {selection}") # Gives PY_VAR0, How to 'decode' PY_VAR0 ?
  20.     # print(f"*selection: {*selection}") # gives and error. Cant use '*' in f-strings
  21.     print(f"selection[0]: {selection[0]}") # gives and error: 'StringVar' object is not subscriptable   
  23. menubar = Menu(root)
  24. stage_menu_item = Menu(menubar, tearoff=0)
  25. menubar.add_cascade(label="Stage", menu=stage_menu_item) # Shows the caption
  26. stage_menu_item.add_command(label="1", command = confirm_stage)
  27. stage_menu_item.add_command(label="2", command = confirm_stage)
  29. root.config(menu=menubar)
  31. root.mainloop()

The "confirm_stage" appears to offer no argument to the called function. It surely can't be that each single item selected has to point to a new separate and unique function specifically written for each item in the menu, although it would work, the code would be unwieldy.

I've seen references to StringVar() which I don't fully understand, and tried to apply it but no joy, and then how would one pass a useful second accompanying variable?

UPDATE 2: - Stripped down code. I need to get the label of the menu item clicked on.

  1. import tkinter as tk
  2. from tkinter import Toplevel, Button, Tk, Menu, Frame
  4. root = Tk()
  5. root.geometry("200x170")
  8. def donation_fn(selection):
  9.     
  10.     a= clicked_r.get()
  11.     print(f"a= {a}")
  12.     print(f"selection= {selection}")
  14.     b= clicked_m.get()
  15.     print(f"b= {b}")
  16.     print(f"selection= {selection}")
  20. menubar = Menu(root)
  22. clicked_r = tk.StringVar(root)
  23. clicked_m = tk.StringVar(menubar)
  25. list=['1 donation', '2 donations', '3 donations']
  27. donation = Menu(menubar, tearoff=0)
  28. menubar.add_cascade(label="Donations", menu=donation) # Shows the caption
  29. for _ in list: donation.add_command(label=_,  command = lambda: donation_fn(clicked_m.get()))
  30. # port_item.add_command(label=list,  command = lambda: None)
  33. root.config(menu=menubar)
  35. root.mainloop()

答案1

得分: 1

  1. 如果你只想将菜单文本传递给回调函数，并且不希望在每次调用`.add_command()`时都这样做，那么你可以创建一个继承自`tk.Menu`的自定义类，并且重写类方法`add_command()`。在重写的`add_command()`方法内部，当执行时，你可以将菜单文本传递给指定的回调函数。
  3. ```python
  4. import tkinter as tk
  6. class MyMenu(tk.Menu):
  7.     def add_command(self, **kwargs):
  8.         callback = kwargs.pop('command', None)
  9.         text = kwargs.get('label')
  10.         # 将菜单文本传递给指定的回调函数
  11.         super().add_command(**kwargs, command=(lambda: callback(text)) if callback else None)
  13. root = tk.Tk()
  15. xr, yr = 200, 170
  16. root.geometry(f"{xr}x{yr}")
  18. def confirm_stage(menu_text):
  19.     print(menu_text)
  21. menubar = tk.Menu(root)
  23. # 使用MyMenu而不是tk.Menu
  24. stage_menu_item = MyMenu(menubar, tearoff=0)
  25. menubar.add_cascade(label="Stage", menu=stage_menu_item)
  26. stage_menu_item.add_command(label="1", command=confirm_stage)
  27. stage_menu_item.add_command(label="2", command=confirm_stage)
  29. root.config(menu=menubar)
  30. root.mainloop()
英文:

If you just want to pass the menu text to the callback and don't want to do it in every call of .add_command(), then you can create a custom class inheriting from tk.Menu and override the class method add_command(). Inside the override add_command(), you can pass the menu text to the given callback when it is being executed.

  1. import tkinter as tk
  3. class MyMenu(tk.Menu):
  4.     def add_command(self, **kwargs):
  5.         callback = kwargs.pop('command', None)
  6.         text = kwargs.get('label')
  7.         # pass the menu text to the given callback
  8.         super().add_command(**kwargs, command=(lambda: callback(text)) if callback else None)
  10. root = tk.Tk()
  12. xr, yr = 200, 170
  13. root.geometry(f"{xr}x{yr}")
  15. def confirm_stage(menu_text):
  16.     print(menu_text)
  18. menubar = tk.Menu(root)
  20. # Use MyMenu instead of tk.Menu
  21. stage_menu_item = MyMenu(menubar, tearoff=0)
  22. menubar.add_cascade(label="Stage", menu=stage_menu_item)
  23. stage_menu_item.add_command(label="1", command=confirm_stage)
  24. stage_menu_item.add_command(label="2", command=confirm_stage)
  26. root.config(menu=menubar)
  27. root.mainloop()

答案2

得分: 0

这是您想要的吗？

  1. import tkinter as tk
  2. from tkinter import Toplevel, Button, Tk, Menu, Frame
  4. root = Tk()
  6. xr, yr = 200, 170
  7. rg = str(xr) + "x" + str(yr)  # 连接字符串
  8. root.geometry(rg)
  10. def confirm_stage(var):
  11.     print(var)
  13. menubar = Menu(root)
  14. stage_menu_item = Menu(menubar, tearoff=0)
  15. menubar.add_cascade(label="Stage", menu=stage_menu_item)
  16. stage_menu_item.add_command(label="1", command=lambda: confirm_stage(1))
  17. stage_menu_item.add_command(label="2", command=lambda: confirm_stage(2))
  19. root.config(menu=menubar)
  21. root.mainloop()

如果需要进一步的帮助，请告诉我。

英文:

Is this what you want?

  1. import tkinter as tk
  2. from tkinter import Toplevel, Button, Tk, Menu, Frame
  4. root = Tk()
  6. xr, yr = 200, 170
  7. rg = str(xr) + "x" + str(yr) # concatinating
  8. root.geometry(rg)
  10. # selection = tk.StringVar()
  12. # print(f"Before option menu selected, selection.get() = {selection.get()}")
  14. # def confirm_stage(*args):
  15. #     global selection
  16. #     print(f"selection.get(): {selection.get()}")
  17. #     print(f"selection: {selection}") # Gives PY_VAR0, How to 'decode' PY_VAR0 ?
  18. #     # print(f"*selection: {*selection}") # gives and error. Cant use '*' in f-strings
  19. #     print(f"selection[0]: {selection[0]}") # gives and error: 'StringVar' object is not subscriptable
  21. def confirm_stage(var):
  22.     print(var)
  24. menubar = Menu(root)
  25. stage_menu_item = Menu(menubar, tearoff=0)
  26. menubar.add_cascade(label="Stage", menu=stage_menu_item) # Shows the caption
  27. # stage_menu_item.add_command(label="1", command = confirm_stage)
  28. # stage_menu_item.add_command(label="2", command = confirm_stage)
  29. stage_menu_item.add_command(label="1", command = lambda: confirm_stage(1))
  30. stage_menu_item.add_command(label="2", command = lambda: confirm_stage(2))
  32. root.config(menu=menubar)
  34. root.mainloop()

答案3

得分: 0

以下是翻译好的部分：

上面提到的“lambda”解决方案，

...
stage_menu_item.add_command(label="1", command = lambda: confirm_stage(1))
...

似乎适用于静态参数，但如果您尝试在循环中使用它，例如：

...
for _x in range(5):
stage_menu_item.add_command(label='Menu'+str(_x), command=lambda: confirm_stage(str(_x)))
...

它不起作用。“_x”始终为“4”，无论您调用哪个菜单项。不知道为什么。

对我而言唯一有效的方法是：

def _set(x:str):
return lambda: confirm_stage(x)

...

for _x in range(5):
stage_menu_item.add_command(label=str(_x), command=_set(str(_x)))

这将产生所需的结果：“0”，“1”，“2”，“3”，“4”

如果有人能告诉我为什么上述简单解决方案（不使用_set函数）不起作用，请继续。

我忘了提到我用tk.Menu替换了MyMenu，因为我不喜欢那种方法。

英文:

The above mentioned "lambda" only solution,

  1. ...
  2. stage_menu_item.add_command(label="1", command = lambda: confirm_stage(1))
  3. ...

seems to work with static parameters, but if you try it with a loop, eg:

  1. ...
  2. for _x in range(5):
  3.    stage_menu_item.add_command(label='Menu'+str(_x), command=lambda: confirm_stage(str(_x)))
  4. ...

It doesn't. "_x" is always "4" no matter what menu item you call. Don't know why.

The only way it worked for me was:

  1. def _set(x:str):
  2.     return lambda: confirm_stage(x)
  4. ...
  6. for _x in range(5):
  7.     stage_menu_item.add_command(label=str(_x), command=_set(str(_x)))

Which renders the wanted result of: "0", "1", "2", "3", "4"

If anyone can enlighten me, why the above easy solution (without _set function) is not working, go ahead.

I forgot to mention I replaced the MyMenu with tk.Menu, since I didn't liked that approach.

huangapple
  • 本文由 发表于 2023年5月13日 23:14:59
  • 转载请务必保留本文链接：https://go.coder-hub.com/76243474.html
  • python
  • tkinter
  • tkinter-menu
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