Turning a Variable into a Function? (Code works, interesting behavior)

Question

I am currently working on a project that involves reading a single character from the command-line without waiting for newlines. I found a helpful answer here, and followed it to its source here. I modified the code slightly, and now I have the following:

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(1)
            finally:
                termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
            return ch

def main():
    inkey = _Getch()
    while(1):
        k=inkey()
        if k!='':break
    print 'you pressed', k

The part that is interesting to me here is the inkey(). I have tried modifying it to k=inkey or k=_Getch, etc. but then it doesn't work as it is meant to. As far as I can tell, no inkey() method had been defined previously, so it seems like the variable inkey=_Getch() is somehow being used as a function.

I don't understand what's going on here. How is this possible? What is the underlying mechanic that is being used? I'd be glad if someone could shed some light on this.

Answer 1

_Getch is a class, and inkey is an instance of the class. It is not a function.

class A:
    pass

a = A() # instantiate an object of class A

You should definitely read the python docs.