Python 文件替换行时添加空格问题及解决方法

• 在进行 Python 编程时，遇到一个问题：在使用 replace_line 函数替换文件中的一行时，会在新行后添加一个空格。
• 想要只在替换后的新行后添加一个空格，而不是在每一行后都添加空格。

2. 解决方案：

   • 问题的原因是 replace_line 函数在替换行时，使用了 out.writelines('\n'.join(lines)) 来写入文件，这会导致在每一行后都添加一个换行符。
   • 为了解决这个问题，需要在 text 变量中包含一个换行符 '\n'，这样才能在替换行时只添加一个空格。
   • 修改后的代码如下：

def replace_line(file_name, line_num, text):
    with open(file_name, 'r') as fin, open(file_name, 'w') as out:
        lines = fin.readlines()
        lines[line_num] = text + '\n'  # This should contain a '\n'
        out.writelines(lines)

• with 语句用于管理文件对象，确保文件在 with 块结束后被正确关闭，即使在发生异常时也是如此。

代码示例：

from tkinter import*              #imports the Tkinter (GUI) library
master = Tk()                   # Creates a Tk root widget to initialize Tkinter


names_list = Listbox(master)                  # Creates the listbox
names_list.pack()

names_list.insert(0,"Print List of Names")
names_list.insert(1,"Add Name")      #This populates the listbox with the different    options
names_list.insert(2,"Change Name")
names_list.insert(3,"Remove Name")
names_list.insert(4,"Quit")

def replace_line(file_name, line_num, text):         # This creates the function that  will erase names
    with open(file_name, 'r') as fin, open(file_name, 'w') as out:
        lines = fin.readlines()
        lines[line_num] = text + '\n'
        out.writelines(lines)

def CurSelect(evt):                   # defines the CurSelect function that will print out the the value latter selected in the listbox
    value=str((names_list.get(names_list.curselection())))

    if value =="Print List of Names":           # What to do if  "Print List of Names" is selected
        names = open("Names.txt",'r')
        for name in names:         #reads names as a list line by line istead of all on one line
            print(name)
        names.close
    else:
        if value == "Add Name":           # What to do if "Add Name" is selected
            names = open("Names.txt",'a')
            new_name=input("Type the name you would like to add and press enter")          # This creates a variable that is passes to file.write for appending
            names.write(new_name)
            names.write("\n")                   # This adds a new line after appending the new_name variable
            names.close
        else:
            if value == "Change Name":           # What to do if "Change Name" is selected
                names = open("Names.txt",'r')
                phrase = input("Enter name to change")         # Looks for the name to change
                for line in names:           # Looks for the line number that the name to change is on
                    if phrase in line:
                        with open("Names.txt",'r') as myFile:
                            for num, line in enumerate(myFile, 0):
                                if phrase in line:              # Actually replaces the name with a new name entered by the user
                                    phrase_change = input("Enter name to change to")
                                    replace_line("Names.txt", num, phrase_change)
                names.close

names_list.bind('<<ListboxSelect>>',CurSelect)       #binds the selection in the listbox to the Curselect function


master.mainloop()                            # Tkinter Event Loop: make the window actually appear

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