如何覆蓋tkinter中的文本文件中的數據

Question

我正在用tkinter創建一個程序，它帶有一個存儲在文本文件中的默認名稱和密碼。登錄後，您需要打開Toplevel窗口，然後輸入您要在後續登錄中使用的名稱和密碼。我定義我的變量，但如果我要覆蓋文本文件我收到如下：

Error "NameError: name 'e1' is not defined"

我知道我已經定義。

import sys 
from tkinter import messagebox 
from tkinter import * 


now = open("pass.txt","w+") 
now.write("user\n") 
now.write("python3") 
now.close() 


def login_in(): 
    with open("pass.txt") as f: 
     new = f.readlines() 
     name = new[0].rstrip() 
     password = new[1].rstrip() 
    if entry1.get() == name and entry2.get() == password: 
     root.deiconify() 
     log.destroy() 
    else: 
     messagebox.showerror("error","login Failed") 


def change_login(): 
    ch = Toplevel(root) 
    ch.geometry('300x300') 
    e1 = Entry(ch, width=20).pack() 
    e2 = Entry(ch, width=20).pack() 
    sb = Button(ch, text="save", command=save_changes).pack() 

def save_changes(): # function to change data in the txt file 
    data = e1.get() + "\n " + e2.get() 
    with open("pass.txt", "w") as f: 
     f.writelines(data) 


root= Tk() 
log = Toplevel() 


root.geometry("350x350") 
log.geometry("200x200") 

entry1 = Entry(log) 
entry2 = Entry(log) 
button1 = Button(log, text="Login", command=login_in) #Login button 

entry1.pack() 
entry2.pack() 
button1.pack() 

label = Label(root, text="welcome").pack() 
butt = Button(root, text="change data in file", command=change_login).pack() 

root.withdraw() 
root.mainloop()  

Answer 1

所以你在這裏有幾個選擇，但總的來說你有兩個主要問題。

第一個問題是在創建e1和e2輸入字段後使用.pack()。這是get()方法的一個問題，因爲如果按此方式打包，幾何體管理器將返回None。正確的方法是首先用e1 = Entry(ch, width=20)創建窗口小部件，然後用e1.pack()將它打包在下一行，這將允許get()在e1上工作。

第二個問題是局部變量與全局變量的問題。您已經在函數change_login()內創建了e1和e2，並且不告訴python e1和e2是全局變量，它會自動假定您希望它們作爲局部變量。這意味着變量只能在創建它們的函數內訪問。

您有幾個選項，我會爲您分解它們。

1）快速和骯髒的選項是將e1和e2作爲全局變量。這可以通過在這種情況下使用global var_name, var2_name, and_so_on所以做這一行添加到您的change_login():和save_changes()功能上：

global e1, e2 

這也告訴Python添加e1和e2到全局命名空間，它將使save_changes()使用全局名稱空間中的變量。

2）另一種方法是使用button命令將2個變量傳遞給save_changes()。我們將需要使用lambda對於這一點，我們可以通過添加做到這一點：

command = lambda e1=e1, e2=e2: save_changes(e1, e2) 

在change_login()創建的按鈕並添加2個參數save_changes()這樣的：

save_changes(e1, e2) 

這只是工作以及第一個選項，它也避免使用全局變量。

3）第三種選擇是將整個程序創建爲一個類，並使用類屬性允許變量與類中的所有方法一起工作。

以下是使用第一個選項代碼的例子：

import sys 
from tkinter import messagebox 
from tkinter import * 

now = open("pass.txt","w+") 
now.write("user\n") 
now.write("python3") 
now.close() 

def login_in(): 
    with open("pass.txt") as f: 
     new = f.readlines() 
     name = new[0].rstrip() 
     password = new[1].rstrip() 
    if entry1.get() == name and entry2.get() == password: 
     root.deiconify() 
     log.destroy() 
    else: 
     messagebox.showerror("error","login Failed") 

def change_login(): 
    global e1, e2 
    ch = Toplevel(root) 
    ch.geometry('300x300') 
    e1 = Entry(ch, width=20) 
    e1.pack() 
    e2 = Entry(ch, width=20) 
    e2.pack() 
    sb = Button(ch, text="save", command=save_changes).pack() 

def save_changes(): # function to change data in the txt file 
    global e1, e2 
    data = e1.get() + "\n" + e2.get() # removed space after \n 
    with open("pass.txt", "w") as f: 
     f.writelines(data) 

root= Tk() 
log = Toplevel() 
root.geometry("350x350") 
log.geometry("200x200") 

entry1 = Entry(log) 
entry2 = Entry(log) 
button1 = Button(log, text="Login", command=login_in) #Login button 

entry1.pack() 
entry2.pack() 
button1.pack() 

label = Label(root, text="welcome").pack() 
butt = Button(root, text="change data in file", command=change_login).pack() 

root.withdraw() 
root.mainloop() 

下面是使用第二個選項的代碼示例：

import sys 
from tkinter import messagebox 
from tkinter import * 

now = open("pass.txt","w+") 
now.write("user\n") 
now.write("python3") 
now.close() 

def login_in(): 
    with open("pass.txt") as f: 
     new = f.readlines() 
     name = new[0].rstrip() 
     password = new[1].rstrip() 
    if entry1.get() == name and entry2.get() == password: 
     root.deiconify() 
     log.destroy() 
    else: 
     messagebox.showerror("error","login Failed") 

def change_login(): 
    ch = Toplevel(root) 
    ch.geometry('300x300') 
    e1 = Entry(ch, width=20) 
    e1.pack() 
    e2 = Entry(ch, width=20) 
    e2.pack() 
    Button(ch, text="save", command=lambda e1=e1, e2=e2: save_changes(e1, e2)).pack() 

def save_changes(e1, e2): # function to change data in the txt file 
    data = e1.get() + "\n" + e2.get() # removed space after \n 
    with open("pass.txt", "w") as f: 
     f.writelines(data) 

root= Tk() 
log = Toplevel() 
root.geometry("350x350") 
log.geometry("200x200") 

entry1 = Entry(log) 
entry2 = Entry(log) 
button1 = Button(log, text="Login", command=login_in) #Login button 

entry1.pack() 
entry2.pack() 
button1.pack() 

label = Label(root, text="welcome").pack() 
butt = Button(root, text="change data in file", command=change_login).pack() 

root.withdraw() 
root.mainloop() 

下面是轉換代碼示例到一個類並使用類屬性來避免使用全局變量。

import sys 
from tkinter import messagebox 
from tkinter import * 


class MyApp(Frame): 

    def __init__(self, master, *args, **kwargs): 
     Frame.__init__(self, master, *args, **kwargs) 

     self.master = master 
     self.master.withdraw() 

     self.log = Toplevel() 
     self.master.geometry("350x350") 
     self.log.geometry("200x200") 

     self.entry1 = Entry(self.log) 
     self.entry2 = Entry(self.log) 
     self.button1 = Button(self.log, text="Login", command=self.login_in) 

     self.entry1.pack() 
     self.entry2.pack() 
     self.button1.pack() 

     Label(root, text="welcome").pack() 
     Button(root, text="change data in file", command=self.change_login).pack() 

    def login_in(self): 
     with open("pass.txt") as f: 
      new = f.readlines() 
      name = new[0].rstrip() 
      password = new[1].rstrip() 
     if self.entry1.get() == name and self.entry2.get() == password: 
      self.master.deiconify() 
      self.log.destroy() 
     else: 
      messagebox.showerror("error","login Failed") 

    def change_login(self): 
     ch = Toplevel(self.master) 
     ch.geometry('300x300') 
     self.e1 = Entry(ch, width=20) 
     self.e1.pack() 
     self.e2 = Entry(ch, width=20) 
     self.e2.pack() 
     Button(ch, text="save", command=self.save_changes).pack() 

    def save_changes(self): 
     data = "{}\n{}".format(self.e1.get(), self.e2.get()) 
     with open("pass.txt", "w") as f: 
      f.writelines(data) 


if __name__ == "__main__": 
    now = open("pass.txt","w+") 
    now.write("user\n") 
    now.write("python3") 
    now.close() 

    root = Tk() 
    app = MyApp(root) 
    root.mainloop()