Finding the Values of the Arrow Keys in Python: Why are they triples?

I think I figured it out.

I learned from here that each arrow key is represented by a unique ANSI escape code. Then I learned that the ANSI escape codes vary by system and application: in my terminal, hitting cat and pressing the up-arrow gives ^[[A, in C it seems to be \033[A, etc. The latter part, the [A, remains the same, but the code for the preceding Escape can be in hex(beginning with an x), octal (beginning with a 0), or decimal(no lead in number).

Then I opened the python console, and plugged in the triples I had previously received, trying to find their character values. As it turned out, chr(27) gave \x1b, chr(91) gave [, and calling chr on 65,66,67,68 returned A,B,C,D respectively. Then it was clear: \x1b was the escape-code!

Then I noted that an arrow key, in ANSI represented as a triple, is of course represented as three characters, so I needed to amend my code so as to read in three characters at a time. Here is the result:

import sys,tty,termios
class _Getch:
    def __call__(self):
            fd = sys.stdin.fileno()
            old_settings = termios.tcgetattr(fd)
            try:
                tty.setraw(sys.stdin.fileno())
                ch = sys.stdin.read(3)
            finally:
                termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
            return ch

def get():
        inkey = _Getch()
        while(1):
                k=inkey()
                if k!='':break
        if k=='\x1b[A':
                print "up"
        elif k=='\x1b[B':
                print "down"
        elif k=='\x1b[C':
                print "right"
        elif k=='\x1b[D':
                print "left"
        else:
                print "not an arrow key!"

def main():
        for i in range(0,20):
                get()

if __name__=='__main__':
        main()