(Windows/DOS only) The msvcrt
module gives you access to a number of
functions in the Microsoft Visual C/C++ Runtime Library (MSVCRT).
Example 12-13 demonstrates the getch
function reading a single keypress from
the console.
The kbhit
function returns true if a key has been
pressed (which means that getch
won’t block), as shown in Example 12-14.
Example 12-14. Using the msvcrt Module to Poll the Keyboard
File: msvcrt-example-2.py import msvcrt import time print "press SPACE to enter the serial number" while not msvcrt.kbhit() or msvcrt.getch() != " ": # do something else print ".", time.sleep(0.1) print # clear the keyboard buffer while msvcrt.kbhit(): msvcrt.getch() serial = raw_input("enter your serial number: ") print "serial number is", serialpress SPACE to enter the serial number
. . . . . . . . . . . . . . . . . . . . . . . .
enter your serial number: 10
serial number is 10
The locking
function in Example 12-15 can be used to implement
cross-process file locking under Windows.
Example 12-15. Using the msvcrt Module for File Locking
File: msvcrt-example-3.py import msvcrt import os LK_UNLCK = 0 # unlock the file region LK_LOCK = 1 # lock the file region LK_NBLCK = 2 # non-blocking lock LK_RLCK = 3 # lock for writing LK_NBRLCK = 4 # non-blocking lock for writing FILE = "counter.txt" if not os.path.exists(FILE): file = open(FILE, "w") file.write("0") file.close() for i in range(20): file = open(FILE, "r+") # look from current position (0) to end of file msvcrt.locking(file.fileno(), LK_LOCK, os.path.getsize(FILE)) counter = int(file.readline()) + 1 file.seek(0) file.write(str(counter)) file.close() # unlocks the file print os.getpid(), "=>", counter time.sleep(0.1)208 => 21
208 => 22
208 => 23
208 => 24
208 => 25
208 => 26
3.133.132.99