如何将变量从一个类调用到另一个类？

Question

我试图将登录类中的变量显示到我的菜单类，但每当我这样做时，我总是得到错误 Object login has no attribute user。

这是我的login.py 文件

 def login(self):
        global con
        user = self.txt_user.get().strip()
        pwd = self.txt_pass.get().strip()
        if user == "" or pwd == "":
            messagebox.showerror("Error", "Please fill up all fields!")
        else:
            try :
                con=pymysql.connect(host="localhost",user="root",password="",database="employee")
                cur=con.cursor()
                cur.execute("select 1 from employeelist where username=%s and password=%s", (user,pwd))
                if cur.rowcount == 1:
                    messagebox.showinfo("Success", "Login Successful", parent=self.root)
                    self.menu()
                else:
                    messagebox.showerror("Error", "Wrong Username or Password. Please try again!")
            except Exception as ex:
                messagebox.showerror("Error",f"Error due to: {str(ex)}",parent=self.root)
            finally:
                con.close()


    def menu(self):
        self.root.destroy()
        menu.MenuForm()

if __name__ == "__main__":
    root = Tk()
    obj = Login(root)
    root.mainloop()

这是我的menu.py 文件

from tkinter import *
from tkinter import ttk, messagebox
import PIL
from PIL import ImageTk
from PIL import Image
import login

class Menu:
    def __init__(self,root):
        self.root = root
        self.root.title("Main Menu")
        self.root.geometry("1350x768+0+0")
        self.root.resizable(False, False)
        self.bg = ImageTk.PhotoImage(file="Images/bgimage.jpg")
        bg = Label(self.root, image=self.bg).place(x=0, y=0, relwidth=1, relheight=1)
        framemenu = Frame(self.root, bg="white")

        framemenu.place(x=350, y=100, height=500, width=700)
        welcometitle = Label(framemenu, text="Welcome " + login.Login.user(), font=("Arial", 30, "bold"), fg="orange", bg="white").place(x=70,y=70)



def MenuForm():
    win = Tk()
    obj = Menu(win)


if __name__ == "__main__":
    root = Tk()
    obj = Menu(root)
    root.mainloop()

我在menu 类中导入了login，但它仍然给我错误对象没有实例。

Answer 1

导入是不够的。 当您使用 objects 时，如果您想使用 object 首先您必须创建一个实例，然后您可以使用该实例，这是一个示例：

class login():
        def __init__(self):
                print("Hi im Login Object")

class main():
        def __init__(self):
                login_obj = login() # Instance created

main()

如您所见，我将 Login 类的实例创建为 main 类，然后它起作用了。

输出：

Hi im Login Object

Answer 2

您可以按照@Hosseinreza 的方法来改进您的代码，但如果您想使用现有代码，请将用户属性传递给菜单类，如下面的代码摘录

def login(self)
   if cur.rowcount == 1:
       messagebox.showinfo("Success", "Login Successful", parent=self.root)
       self.menu(user)

def menu(self, user):
        self.root.destroy()
        menu.MenuForm(user)

然后在 Menu 类中，您可以如下使用它：

from tkinter import *
from tkinter import ttk, messagebox
import PIL
from PIL import ImageTk
from PIL import Image

class Menu:
    def __init__(self,root, user):
        self.root = root
        self.root.title("Main Menu")
        self.root.geometry("1350x768+0+0")
        self.root.resizable(False, False)
        self.bg = ImageTk.PhotoImage(file="Images/bgimage.jpg")
        bg = Label(self.root, image=self.bg).place(x=0, y=0, relwidth=1, relheight=1)
        framemenu = Frame(self.root, bg="white")

        framemenu.place(x=350, y=100, height=500, width=700)
        welcometitle = Label(framemenu, text="Welcome " + user, font=("Arial", 30, "bold"), fg="orange", bg="white").place(x=70,y=70)



def MenuForm(user):
    win = Tk()
    obj = Menu(win, user)


if __name__ == "__main__":
    root = Tk()
    obj = Menu(root)
    root.mainloop()

Answer 3

最好通过参数将用户传递给menu.MenuForm()：

class Login:
    ...

    def login(self):
        user = self.txt_user.get().strip()
        pwd = self.txt_pass.get().strip()
        if user == "" or pwd == "":
            messagebox.showerror("Error", "Please fill up all fields!")
        else:
            try :
                con=pymysql.connect(host="localhost",user="root",password="",database="employee")
                cur=con.cursor()
                cur.execute("select 1 from employeelist where username=%s and password=%s", (user,pwd))
                if cur.rowcount == 1:
                    messagebox.showinfo("Success", "Login Successful", parent=self.root)
                    self.menu(user) # pass user to self.menu()
                else:
                    messagebox.showerror("Error", "Wrong Username or Password. Please try again!")
            except Exception as ex:
                messagebox.showerror("Error",f"Error due to: {str(ex)}",parent=self.root)
            finally:
                con.close()

    def menu(self, user):
        self.root.destroy()
        menu.MenuForm(user) # pass user to menu.MenuForm()

---

menu.py:

from tkinter import *
#from tkinter import ttk, messagebox
from PIL import Image, ImageTk

class Menu:
    def __init__(self, root, user): # user passed as argument
        self.root = root
        self.root.title("Main Menu")
        self.root.geometry("1350x768+0+0")
        self.root.resizable(False, False)
        self.bg = ImageTk.PhotoImage(file="Images/bgimage.jpg")
        bg = Label(self.root, image=self.bg).place(x=0, y=0, relwidth=1, relheight=1)
        framemenu = Frame(self.root, bg="white")

        framemenu.place(x=350, y=100, height=500, width=700)
        welcometitle = Label(framemenu, text="Welcome " + user, font=("Arial", 30, "bold"), fg="orange", bg="white").place(x=70,y=70)

def MenuForm(user): # user passed as argument
    win = Tk()
    obj = Menu(win, user) # pass user to `Menu` class

if __name__ == "__main__":
    root = Tk()
    obj = Menu(root, "user")
    root.mainloop()