在Python中删除文件行

我正在尝试创建一个接受用户名和高分的程序，如果他们已经是用户，他们会更新到新的高分，或者如果不是，则仅添加高分。

我的代码是：

try:
    a = open("data", "r+")
except FileNotFoundError:
    a = open("data", "w")
a = open("data", "r+")
b = a.read()
user = input("Username: ")
user2 = list(user)
if user in b:
    old = input("What is your old highscore? ")
    new = input("What is your new highscore? ")
    b2 = b.split()
    for line in b2:
        #Where I want to edit.
        line=line.replace(old, new)
        print(line)

else:
    new = input("What is your highscore? ")
    a.write(user + " " + new + "\n")
a.close()

有谁知道如何用文件中的新内容替换旧内容？

简单的答案是：不可能。操作系统及其文件操作没有“行”的概念。它们处理二进制数据块。一些库（例如 Python 的标准库）为reading上面的行 - 但它们不允许您寻址单独的行。

那么如何解决问题呢？只需打开文件，读取所有行，就地操作有问题的行，然后写入whole再次归档。

 import tempfile

 highscore_file = tempfile.mktemp()

 with open(highscore_file, "w") as outf:
     outf.write("peter 1000\nsarah 500\n")

 player = "sarah"
 score = 2000

 output_lines = []
 with open(highscore_file) as inf:
     for line in inf:
         if player in line:
             # replace old with new line. Don't forget trailing newline!
             line = "%s %i\n" % (player, score)
         output_lines.append(line)

 with open(highscore_file, "w") as outf:
     outf.write("".join(output_lines))



 with open(highscore_file) as inf:
     print inf.read()