英文:
Why isn't my text widget getting cleared with the delete function?
问题
我正在使用tkinter构建一个菜单，其中有不同的按钮用于前菜（Entrees）、主菜（Mains）和甜点（Desserts）。当您单击某个按钮时，菜单项应该更改以反映当前选择，然而，我在我的printItems函数中使用的.delete()似乎不起作用。程序默认停留在前菜（Entrees）菜单上。
#设置 - TKinterimport tkinter as tkw = tk.Tk()w.title("交互式餐厅菜单")w.geometry("640x640")w.resizable(False,False)w['bg'] = 'black'#设置 - SQLimport mysql.connector as mccon = mc.connect(user='root', host='localhost', password='Cars!234', database='Zayan')cur = con.cursor()#打印菜单项v = tk.Scrollbar(orient='vertical')items = tk.Text(bg='black', font=('Baskerville', 18), wrap=tk.WORD, yscrollcommand=v.set)items.grid(column=0, row=2, columnspan=4, padx=20)def getItem(ID, course):currentItem = []table_name = "Menu" + coursequery = "SELECT Item, Price, Description FROM {} WHERE ID = %s".format(table_name)cur.execute(query, (ID,))result = cur.fetchone()currentItem.append(result[0] + ' (' + str(result[1]) + '$)')currentItem.append(result[2])return currentItemdef printItems(course):items.delete(1.0, 'end')cur.execute("SELECT MAX(ID) FROM {}".format("Menu" + course))n = cur.fetchone()for i in range(1, n[0] + 1):items.insert(tk.END, '\n\n' + str(i) + "." + getItem(i, course)[0] + '\n' + getItem(i, course)[1])items.config(state='disabled', highlightthickness=0)#标题和按钮head = tk.Label(text="菜单", font=("Garamond", 40), bg='black')head.grid(column=0, row=0, columnspan=4, sticky='N', pady=10)app = tk.Button(text="前菜", width=12, height=2, command=lambda: printItems('Entree'))main = tk.Button(text="主菜", width=12, height=2, command=lambda: printItems("Main"))des = tk.Button(text="甜点", width=12, height=2)deal = tk.Button(text="特惠套餐", width=12, height=2)app.grid(column=0, row=1, padx=8)main.grid(column=1, row=1, padx=8)des.grid(column=2, row=1, padx=8)deal.grid(column=3, row=1, padx=8)w.grid_columnconfigure((0, 1, 2, 3), weight=1)w.mainloop()
请注意，我对"前菜"和"主菜"按钮的命令使用了lambda函数，以便在单击按钮时才调用printItems函数，而不是在创建按钮时立即调用它。这样可以确保单击按钮时才会更新菜单项。
英文:
I am building a menu using tkinter which has different buttons for Entrees, Mains and Desserts. When you click a certain button the menu items should change to reflect that however the .delete() I am using in my printItems function doesn't seem to be working. The program is stuck on the Entrees menu by default
#Setup - TKinterimport tkinter as tkw = tk.Tk()w.title("Interactive Restaurant Menu")w.geometry("640x640")w.resizable(False,False)w['bg'] = 'black'#Setup - SQLimport mysql.connector as mccon = mc.connect(user = 'root',host = 'localhost', password = 'Cars!234',database = 'Zayan')cur = con.cursor()#Printing Menu Itemsv = tk.Scrollbar( orient='vertical')items = tk.Text(bg = 'black',font = ('Baskerville', 18),wrap = tk.WORD,yscrollcommand = v.set)items.grid(column = 0,row = 2, columnspan = 4,padx = 20)def getItem(ID, course):currentItem = []table_name = "Menu" + coursequery = "SELECT Item,Price,Description FROM {} WHERE ID = %s".format(table_name)cur.execute(query, (ID,))result = cur.fetchone()currentItem.append(result[0] + ' (' + str(result[1]) + '$)')currentItem.append(result[2])return currentItemdef printItems(course):items.delete(1.0,'end')cur.execute("select max(ID) from {}".format("Menu" + course))n = cur.fetchone()for i in range(1,n[0] + 1):items.insert(tk.END,'\n\n' + str(i) + "." + getItem(i,course)[0] + '\n' + getItem(i,course)[1])items.config(state='disabled',highlightthickness=0)#Title And Buttonshead = tk.Label(text = "Menu",font = ("Garamond",40),bg = 'black')head.grid(column = 0,row = 0,columnspan = 4, sticky = 'N', pady = 10)app = tk.Button(text="Entrees",width = 12,height = 2,command = printItems('Entree'))main = tk.Button(text="Mains",width = 12,height = 2,command = printItems("Main"))des = tk.Button(text="Desserts",width = 12,height = 2)deal = tk.Button(text="Deals",width = 12,height = 2)app.grid(column = 0, row = 1,padx = 8)main.grid(column = 1, row = 1,padx = 8)des.grid(column = 2, row = 1,padx = 8)deal.grid(column = 3, row = 1,padx = 8)w.grid_columnconfigure((0,1,2,3), weight=1)w.mainloop()
答案1
得分: 1
问题出在你如何绑定 printItems 函数的地方：
app = tk.Button(text="Entrees", width=12, height=2, command=printItems('Entree'))main = tk.Button(text="Mains", width=12, height=2, command=printItems("Main"))
这两个按钮的 command 参数应该改成 lambda 表达式，这样你可以像这样传递正确的字符串参数给 printItems 函数：
app = tk.Button(text="Entrees", width=12, height=2, command=lambda: printItems('Entree'))main = tk.Button(text="Mains", width=12, height=2, command=lambda: printItems("Main"))
不同之处在于，如原始写法所示，当你实例化 tk.Button 对象时，printItems 会立即被调用，这不是你想要的。相反，将它们包装在 lambda 表达式中会将它们变成所谓的“匿名函数” - 基本上，你告诉它在需要时调用运行你的函数的 lambda，而不是直接调用它。
英文:
The issue lies in how you're binding printItems here:
app = tk.Button(text="Entrees",width = 12,height = 2,command = printItems('Entree'))main = tk.Button(text="Mains",width = 12,height = 2,command = printItems("Main"))
The command parameter for each of these buttons should be made into a lambda so that you can pass the appropriate string argument to printItems like so:
app = tk.Button(text="Entrees", width=12, height=2, command=lambda: printItems('Entree'))main = tk.Button(text="Mains", width=12, height=2, command=lambda: printItems("Main"))
The difference is that as-written, printItems is being called immediately when you instantaite your tk.Button objects, which isn't what you want. Instead, wrapping them in a lambda expression turns them into so-called "anonymous functions" - basically, you're telling it to call the lambda that runs your function for you as-needed, instead of calling it directly.
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