How do I wait for a pressed key?

In Python 3, use input():

input("Press Enter to continue...")

In Python 2, use raw_input():

raw_input("Press Enter to continue...")

This only waits for the user to press enter though.

On Windows/DOS, one might want to use msvcrt. The msvcrt module gives you access to a number of functions in the Microsoft Visual C/C++ Runtime Library (MSVCRT):

import msvcrt as m
def wait():
    m.getch()

This should wait for a key press.

Notes:

In Python 3, raw_input() does not exist.
In Python 2, input(prompt) is equivalent to eval(raw_input(prompt)).

In Python 3, use input():

input("Press Enter to continue...")

In Python 2, use raw_input():

raw_input("Press Enter to continue...")

On my linux box, I use the following code. This is similar to code I've seen elsewhere (in the old python FAQs for instance) but that code spins in a tight loop where this code doesn't and there are lots of odd corner cases that code doesn't account for that this code does.

def read_single_keypress():
    """Waits for a single keypress on stdin.

    This is a silly function to call if you need to do it a lot because it has
    to store stdin's current setup, setup stdin for reading single keystrokes
    then read the single keystroke then revert stdin back after reading the
    keystroke.

    Returns a tuple of characters of the key that was pressed - on Linux, 
    pressing keys like up arrow results in a sequence of characters. Returns 
    ('\x03',) on KeyboardInterrupt which can happen when a signal gets
    handled.

    """
    import termios, fcntl, sys, os
    fd = sys.stdin.fileno()
    # save old state
    flags_save = fcntl.fcntl(fd, fcntl.F_GETFL)
    attrs_save = termios.tcgetattr(fd)
    # make raw - the way to do this comes from the termios(3) man page.
    attrs = list(attrs_save) # copy the stored version to update
    # iflag
    attrs[0] &= ~(termios.IGNBRK | termios.BRKINT | termios.PARMRK
                  | termios.ISTRIP | termios.INLCR | termios. IGNCR
                  | termios.ICRNL | termios.IXON )
    # oflag
    attrs[1] &= ~termios.OPOST
    # cflag
    attrs[2] &= ~(termios.CSIZE | termios. PARENB)
    attrs[2] |= termios.CS8
    # lflag
    attrs[3] &= ~(termios.ECHONL | termios.ECHO | termios.ICANON
                  | termios.ISIG | termios.IEXTEN)
    termios.tcsetattr(fd, termios.TCSANOW, attrs)
    # turn off non-blocking
    fcntl.fcntl(fd, fcntl.F_SETFL, flags_save & ~os.O_NONBLOCK)
    # read a single keystroke
    ret = []
    try:
        ret.append(sys.stdin.read(1)) # returns a single character
        fcntl.fcntl(fd, fcntl.F_SETFL, flags_save | os.O_NONBLOCK)
        c = sys.stdin.read(1) # returns a single character
        while len(c) > 0:
            ret.append(c)
            c = sys.stdin.read(1)
    except KeyboardInterrupt:
        ret.append('\x03')
    finally:
        # restore old state
        termios.tcsetattr(fd, termios.TCSAFLUSH, attrs_save)
        fcntl.fcntl(fd, fcntl.F_SETFL, flags_save)
    return tuple(ret)

If you are ok with depending on system commands you can use:

from __future__ import print_function
import os
import platform

if platform.system() == "Windows":
    os.system("pause")
else:
    os.system("/bin/bash -c 'read -s -n 1 -p \"Press any key to continue...\"'")
    print()

It has been verified to work with Python 2 and 3 on Windows, Linux and Mac OS X.