Backspace does not erase in stdout

[Steven D'Aprano]

I have a function which reads characters from stdin and writes stars to 
stdout, but backspacing does not erase the stars as I expected.

Tested in Python 2.6 on Linux. This will almost certainly not work on 
Windows.

import sys, tty, termios
def getpass():
    fd = sys.stdin.fileno()
    old_settings = termios.tcgetattr(fd)
    chars = []
    try:
        tty.setraw(sys.stdin.fileno())
        while 1:
            c = sys.stdin.read(1)
            if c in '\n\r':  # Enter or Return key.
                break
            elif c == '\x7f':  # Backspace key.
                if chars:
                    # Rubout previous character.
                    sys.stdout.write('\b')
                    sys.stdout.flush()
                    del chars[-1]
            else:
                # Obfuscate the letter typed.
                sys.stdout.write('*')
                chars.append(c)
    finally:
        termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
        sys.stdout.write('\n')
    return ''.join(chars)


When I call this function and then type, I get a serious of asterisks as 
expected. Each time I press the backspace key, the cursor moves one 
character to the left, but the asterisks remain visible.

Is there a way to erase the character other than backspacing, writing a 
space, then backspacing again? That feels inelegant.



-- 
Steven