CODEWITHSUNDEEP
pythonraw-input
Lujeen
Lujeen

Reputation: 5

if statement including raw_input just prints whatever i type in to the keyboard

I am very new to python and programming in general and I want to print out the string "forward" whenever i press "w" on the keyboard. It is a test which I will transform into a remote control for a motorized vehicle.

while True:
    if raw_input("") == "w":
        print "forward"

Why does it just print out every key I type?

Upvotes: 0

Views: 74

Answers (2)

user2357112
user2357112

Reputation: 280236

raw_input reads an entire line of input. The line you're inputting is made visible to you, and you can do things like type some text:

aiplanes

go left a few characters to fix your typo:

airplanes

go back to the end and delete a character because you didn't mean to make it plural:

airplane

and then hit Enter, and raw_input will return "airplane". It doesn't just return immediately when you hit a keyboard key.

If you want to read individual keys, you'll need to use lower-level terminal control routines to take input. On Unix, the curses module would be an appropriate tool; I'm not sure what you'd use on Windows. I haven't done this before, but on Unix, I think you'd need to set the terminal to raw or cbreak mode and take input with window.getkey() or window.getch(). You might also have to turn off echoing with curses.noecho(); I'm not sure whether that's included in raw/cbreak mode.

Upvotes: 1

user161778
user161778

Reputation: 534

In Python 2.x the raw_input function will display all characters pressed, and return upon receiving a newline. If you want different behaviour you'll have to use a different function. Here's a portable version of getch for Python, it will return every key press:

# Copied from: stackoverflow.com/questions/510357/python-read-a-single-character-from-the-user
def _find_getch():
    try:
        import termios
    except ImportError:
        # Non-POSIX. Return msvcrt's (Windows') getch.
        import msvcrt
        return msvcrt.getch

    # POSIX system. Create and return a getch that manipulates the tty.
    import sys, tty
    def _getch():
        fd = sys.stdin.fileno()
        old_settings = termios.tcgetattr(fd)
        try:
            tty.setraw(fd)
            ch = sys.stdin.read(1)
        finally:
            termios.tcsetattr(fd, termios.TCSADRAIN, old_settings)
        return ch

    return _getch

getch = _find_getch()

It can be used like so:

while True:
    if getch() == "w":
        print "forward"

Upvotes: 2

Related Questions