Question

您好，我目前正在使用4个组合框。当我检查组合框是否返回组合框的值时，它将引发tkinter异常。

我尝试使用Google搜索问题，并对代码进行了一些调整，但没有一个帮助：

import sys
import tkinter.messagebox as box
from tkinter.filedialog import asksaveasfile
if sys.version_info[0] >= 3:
    import tkinter as tk
    import tkinter.ttk as ttk
else:
    import Tkinter as tk


class App(tk.Frame):

    def __init__(self, master):
        tk.Frame.__init__(self, master)

        self.dict = {'Japan': ['Yokohama', 'Kobe', 'Tokyo'],
                     'China': ['Ningbo', 'Shanghai', 'Hefei'],
                     'USA': ['Baltimore', 'Long Beach', 'Chicago'],
                     'Russia': ['Moscow']}
        self.i = ["EXW", "FOB", "DAT"]
        self.c = ["40ton", "20ton", "Other"]

        self.variable_c = tk.StringVar(self)
        self.variable_i = tk.StringVar(self)
        self.variable_a = tk.StringVar(self)
        self.variable_b = tk.StringVar(self)
        self.last_county = tk.StringVar(self)
        self.area = tk.StringVar(self)
        self.country = tk.StringVar(self)
        self.incoterm = tk.StringVar(self)
        self.capacity = tk.StringVar(self)

        self.variable_b.trace('w', self.fun2)
        self.variable_a.trace('w', self.update_options)
        self.variable_i.trace('w', self.fun3)
        self.variable_c.trace('w', self.fun4)

        self.combobox_i = ttk.Combobox(self, values=list(self.i), 
        state='readonly')
        self.combobox_i.bind("<<ComboboxSelected>>", self.fun3)
        self.combobox_i.current(0)

        self.combobox_c = ttk.Combobox(self, values=list(self.c), 
        state='readonly')
        self.combobox_c.bind("<<ComboboxSelected>>", self.fun4)
        self.combobox_c.current(0)

        self.combobox_a = ttk.Combobox(self, 
        values=list(self.dict.keys()), state='readonly')
        self.combobox_a.bind("<<ComboboxSelected>>", self.fun)
        self.combobox_a.current(0)

        self.combobox_b = ttk.Combobox(self, values=self.dict['Japan'], 
        state='readonly')
        self.combobox_b.bind("<<ComboboxSelected>>", self.fun2)
        self.combobox_b.current(0)




        self.button = ttk.Button(self, text="Check", command=lambda : 
        sample(self.area, self.country, self.incoterm, self.capacity))




        self.combobox_i.pack()
        self.combobox_c.pack()

        self.combobox_a.pack()
        self.combobox_b.pack()
        self.button.pack()
        self.pack()

    def fun(self,*args):
        print("changed 1-st combobox value to: " + self.combobox_a.get())
        if self.last_county != self.combobox_a.get():
        self.combobox_b['values']=self.dict[self.combobox_a.get()]
        self.combobox_b.current(0)
        self.last_county = self.country = self.combobox_a.get()
        return self.variable_a.get()

    def fun2(self, *args):
        print("changed 2-nd combobox value to" + self.combobox_b.get())
        self.area = self.combobox_b.get()
        return self.variable_b.get()

    def fun3(self, *args):
        print("changed 3-rd combobox value to" + self.combobox_i.get())
        self.incoterm = self.combobox_i.get()
        return self.variable_i.get()

    def fun4(self, *args):
        print("changed 4-tth combobox value to" + self.combobox_c.get())
        self.capacity = self.combobox_c.get()
        return self.variable_c.get()


    def update_options(self, *args):
        countries = self.dict[self.variable_a.get()]
        self.variable_b.set(countries[0])

        menu = self.combobox_b['menu']
        menu.delete(0, 'end')

        for country in countries:
            menu.add_command(label=country, command=lambda 
            nation=country: self.variable_b.set(nation))


def sample(area, country, incoterm, capacity):
    box.showinfo('info', 'Selected area: ' + area + '\nSelected country: 
    ' + country + '\nSelected incoterm:' + incoterm
      + '\nSelected capacity' + capacity)

if __name__ == "__main__":
    root = tk.Tk()
    app = App(root)
    app.mainloop()

当我运行程序并单击检查按钮时，它会显示：

Exception in Tkinter callback
Traceback (most recent call last):
File "C:\Users\IDL Mongolia\AppData\Local\Programs\Python\Python37- 
32\lib\tkinter\__init__.py", line 1705, in __call__
return self.func(*args)
File "D:/IDLMongolia's/Desktop/Project/Count_Incoterms.py", line 57, in 
<lambda>
self.button = ttk.Button(self, text="Check", command=lambda : 
sample(self.area, self.country, self.incoterm, self.capacity))
File "D:/IDLMongolia's/Desktop/Project/Count_Incoterms.py", line 107, in 
sample
+ '\nSelected capacity' + capacity)
TypeError: can only concatenate str (not "StringVar") to str

Process finished with exit code 0

请帮帮我。

Answer 1

您正在尝试连接字符串和%。要从StringVar获取字符串，请使用StringVar方法。

最简单的方法是将字符串传递给get时调用get。这样，样本就不需要了解sample了。

StringVar

我会在代码的其他地方寻找问题，因为这些sample(self.area.get(), self.country.get(), self.incoterm.get(), self.capacity.get()))变量之一是从字符串分配给的。如果您更改选项然后单击检查按钮，则会导致异常。

您的代码中肯定还有其他问题，但这可以解决问题中的那个问题。

Answer 2

错误是不言自明的-您正在尝试将StringVar对象与字符串连接起来。

通常，您需要在get上使用StringVar方法来检索其值。但是我注意到您实际上甚至不需要StringVar，也没有以任何方式设置或更改其值。

要正确解决您的错误-只是不要首先创建StringVars。而是将它们设置为空白字符串。

class App(tk.Frame):

    def __init__(self, master):
        tk.Frame.__init__(self, master)
        ...
        self.area = ""
        self.country = ""
        self.incoterm = ""
        self.capacity = ""

我真正建议的是根本不要创建虚拟变量。您始终可以直接通过“ combobox.get（）”来检索值。

class App(tk.Frame):

    def __init__(self, master):
        tk.Frame.__init__(self, master)
        ...
        #self.area = ""
        #self.country = ""
        #self.incoterm = ""
        #self.capacity = ""

        self.button = ttk.Button(self, text="Check", command=lambda : sample(self.combobox_a.get(), self.combobox_b.get(), self.combobox_i.get(), self.combobox_c.get()))

        ...

如何处理“只能将str（而不是“ StringVar”）连接到str”

2 个答案: