从 tkinter OptionMenu 获取值

Question

1 我从OptionMenu 中选择了值

2 点击按钮

但是回调 function 会parse OptionMenu 的打印默认值。 我做错了什么？

我的代码

from tkinter import *
from functools import partial


def parse(shop, city):
    print(f"Parse {city} {shop}") # prints "all shops" but i expected "magnit" because i chosed it


master = Tk()

variable_shop = StringVar(master)
variable_shop.set("all shops") # default value

w = OptionMenu(master, variable_shop, "all shops", "5ka", "magnit", "three").pack()

variable_city = StringVar(master)
variable_city.set("all cities") # default value
w2 = OptionMenu(master, variable_city, "all cities", "Moscow", "Saint Petersburg").pack()

callback = partial(parse, variable_shop.get(), variable_city.get())
b1 = Button(text="Run with values from OptionMenu", command=callback).pack()

mainloop()

Answer 1

您的回调行在程序启动时运行，因此它会在启动时保存值。 当用户单击按钮时，您需要将那些 get() 调用移动到稍后运行的某个地方。 将它们放入解析 function 是有道理的，并且也消除了对部分的需要。

from tkinter import *

def parse():
    city = variable_city.get()
    shop = variable_shop.get()
    print(f"Parse {city} {shop}") 

master = Tk()

variable_shop = StringVar(master)
variable_shop.set("all shops") # default value

OptionMenu(master, variable_shop, "all shops", "5ka", "magnit", "three").pack()

variable_city = StringVar(master)
variable_city.set("all cities") # default value
OptionMenu(master, variable_city, "all cities", "Moscow", "Saint Petersburg").pack()

Button(text="Run with values from OptionMenu", command=parse).pack()

mainloop()

Answer 2

考虑这行代码：

callback = partial(parse, variable_shop.get(), variable_city.get())

它在功能上与此相同：

shop = variable_shop.get()
city = variable_city.get()
callback = partial(parse, shop, city)

换句话说，您在创建get方法大约一毫秒后调用它，而不是等到用户单击按钮。

您根本不需要使用partial 。 只需让回调调用常规 function，并让 function 检索值。 这将使代码更容易编写、更容易理解和更容易调试。

def parse():
    shop = variable_shop.get()
    city = variable_city.get()
    print(f"Parse {city} {shop}") 
...
b1 = Button(text="Run with values from OptionMenu", command=parse)
b1.pack()