python - Writing to a new file if it doesn't exist, and appending to a file if it does

Question

I have a program which writes a user's highscore to a text file. The file is named by the user when they choose a playername.

If the file with that specific username already exists, then the program should append to the file (so that you can see more than one highscore). And if a file with that username doesn't exist (for example, if the user is new), it should create a new file and write to it.

Here's the relevant, so far not working, code:

try: 
    with open(player): #player is the varible storing the username input
        with open(player, 'a') as highscore:
            highscore.write("Username:", player)

except IOError:
    with open(player + ".txt", 'w') as highscore:
        highscore.write("Username:", player)

The above code creates a new file if it doesn't exist, and writes to it. If it exists, nothing has been appended when I check the file, and I get no errors.

Answer 1

Have you tried mode 'a+'?

with open(filename, 'a+') as f:
    f.write(...)

Note however that f.tell() will return 0 in Python 2.x. See https://bugs.python.org/issue22651 for details.