Python如何继续写入文件而不擦除已存在的内容

Question

在Windows中编写我的python 3.3程序，我遇到了一个小问题。我正在试图写一些指令到一个文件，以便程序执行。但是，每次我file.write（）下一行时，它会替换上一行。我希望能够尽可能多地写入这个文件。注意：使用“\ n”似乎不起作用，因为您不知道将会有多少行。请帮忙！这里是我的代码（即一个循环，我不运行这个多次）：

menu = 0 
while menu != None: 
    menu = lipgui.choicebox("Select an option:", choices=["choice1", "choice2", "choice3"]) 
    file = open("file.txt", "w") 
    if menu == "choice1": 
     text_to_write = lipgui.enterbox("Text to write:") 
     file.write(text_to_write) 

Answer 1

每当你打开文件进行写它被删除（截断）时间。打开文件替代，或打开文件只需一次并保持打开状态。

要打开文件进行追加，使用a代替w的模式：

while menu != None: 
    menu = lipgui.choicebox("Select an option:", choices=["choice1", "choice2", "choice3"]) 
    file = open("file.txt", "a") 
    if menu == "choice1": 
     text_to_write = lipgui.enterbox("Text to write:") 
     file.write(text_to_write) 

或打开文件循环外：

file = open("file.txt", "w") 

while menu != None: 
    menu = lipgui.choicebox("Select an option:", choices=["choice1", "choice2", "choice3"]) 
    if menu == "choice1": 
     text_to_write = lipgui.enterbox("Text to write:") 
     file.write(text_to_write) 

或只有一次在第一时间你需要它：

file = None 

while menu != None: 
    menu = lipgui.choicebox("Select an option:", choices=["choice1", "choice2", "choice3"]) 
    if file is None: 
     file = open("file.txt", "w") 
    if menu == "choice1": 
     text_to_write = lipgui.enterbox("Text to write:") 
     file.write(text_to_write)