从文本文件到列表框的偶数行-Python

Question

I have a username-password login system and would like to add a delete user function. The usernames are stored on the even lines of a text file (inc zero) and the passwords on odd numbered lines. Is there a way of adding only the even numbered lines to a listbox to be selected via curselection to be deleted as showing the passwords would be against the point. I currently have all of the contents of the text file showing in the listbox however would like only the usernames to be shown. To delete the lines I have copied the contents of the listbox to a new text file after removing the chosen line from the listbox. Would there also be a way to delete the corresponding password after the username to be deleted has been selected ?

def DelUser():

    global rootDU
    global listbox

    rootDU = Tk()
    rootDU.title('Delete user')

    users = open(creds, 'r')
    mylist = users.readlines()
    users.close()

    listbox = Listbox(rootDU, width=50, height=6)
    listbox.grid(row=0, column=0)
    yscroll = Scrollbar(command=listbox.yview, orient=VERTICAL)
    yscroll.grid(row=0, column=1, sticky=N + S)
    listbox.configure(yscrollcommand=yscroll.set)

    enter1 = Label(rootDU, text='Click on the user to delete', width=50)
    enter1.grid(row=1, column=0)

    for item in mylist:
        listbox.insert(END, item)

    delButton = Button(rootDU, text='Delete', command=RemoveUser)
    delButton.grid(columnspan=2, sticky=W)
    delButton.grid(row=2, column=0)

def RemoveUser():

    global listbox

    try:
        index = listbox.curselection()[0]
        listbox.delete(index)
        os.remove(creds)
        newfile = 'tempfile.txt'
        with open(newfile, 'w') as f:
            f.write(''.join(listbox.get(0, END)))
            f.close()

    except IndexError:
        pass

Answer 1

Just add only every second line to your listbox:

for item in mylist[::2]:
    listbox.insert(END, item)

The ::2 slice picks every second line, starting at line 0. See Explain Python's slice notation for further details.

You then still have to re-read the file to find the corresponding password however, since you don't store that information separately. You really want to store a mapping from usernames to passwords (separately, as information you share between DelUser and RemoveUser ) so you can easily re-write your user file with the remaining users and passwords.

You could also consider using a different format for your file; writing usernames and passwords on the same line , but putting a delimiter character between them, would make it easier to process the data.