Exemple non bloquant et multithread:
Comme le blocage de la saisie au clavier (depuis les input()blocs fonctionnels) n'est souvent pas ce que nous voulons faire (nous aimerions souvent continuer à faire d'autres choses), voici un exemple multithread très simplifié pour montrer comment continuer à exécuter votre application principale tout en lisant les entrées du clavier à chaque fois qu'elles arrivent .
Cela fonctionne en créant un thread à exécuter en arrière-plan, en appelant continuellement input()et en passant toutes les données qu'il reçoit à une file d'attente.
De cette façon, votre thread principal doit faire tout ce qu'il veut, recevant les données d'entrée du clavier du premier thread chaque fois qu'il y a quelque chose dans la file d'attente.
1. Exemple de code Bare Python 3 (sans commentaires):
import threading
import queue
import time
def read_kbd_input(inputQueue):
print('Ready for keyboard input:')
while (True):
input_str = input()
inputQueue.put(input_str)
def main():
EXIT_COMMAND = "exit"
inputQueue = queue.Queue()
inputThread = threading.Thread(target=read_kbd_input, args=(inputQueue,), daemon=True)
inputThread.start()
while (True):
if (inputQueue.qsize() > 0):
input_str = inputQueue.get()
print("input_str = {}".format(input_str))
if (input_str == EXIT_COMMAND):
print("Exiting serial terminal.")
break
# Insert your code here to do whatever you want with the input_str.
# The rest of your program goes here.
time.sleep(0.01)
print("End.")
if (__name__ == '__main__'):
main()
2. Même code Python 3 que ci-dessus, mais avec de nombreux commentaires explicatifs:
"""
read_keyboard_input.py
Gabriel Staples
www.ElectricRCAircraftGuy.com
14 Nov. 2018
References:
- https://pyserial.readthedocs.io/en/latest/pyserial_api.html
- *****https://www.tutorialspoint.com/python/python_multithreading.htm
- *****https://en.wikibooks.org/wiki/Python_Programming/Threading
- /programming/1607612/python-how-do-i-make-a-subclass-from-a-superclass
- https://docs.python.org/3/library/queue.html
- https://docs.python.org/3.7/library/threading.html
To install PySerial: `sudo python3 -m pip install pyserial`
To run this program: `python3 this_filename.py`
"""
import threading
import queue
import time
def read_kbd_input(inputQueue):
print('Ready for keyboard input:')
while (True):
# Receive keyboard input from user.
input_str = input()
# Enqueue this input string.
# Note: Lock not required here since we are only calling a single Queue method, not a sequence of them
# which would otherwise need to be treated as one atomic operation.
inputQueue.put(input_str)
def main():
EXIT_COMMAND = "exit" # Command to exit this program
# The following threading lock is required only if you need to enforce atomic access to a chunk of multiple queue
# method calls in a row. Use this if you have such a need, as follows:
# 1. Pass queueLock as an input parameter to whichever function requires it.
# 2. Call queueLock.acquire() to obtain the lock.
# 3. Do your series of queue calls which need to be treated as one big atomic operation, such as calling
# inputQueue.qsize(), followed by inputQueue.put(), for example.
# 4. Call queueLock.release() to release the lock.
# queueLock = threading.Lock()
#Keyboard input queue to pass data from the thread reading the keyboard inputs to the main thread.
inputQueue = queue.Queue()
# Create & start a thread to read keyboard inputs.
# Set daemon to True to auto-kill this thread when all other non-daemonic threads are exited. This is desired since
# this thread has no cleanup to do, which would otherwise require a more graceful approach to clean up then exit.
inputThread = threading.Thread(target=read_kbd_input, args=(inputQueue,), daemon=True)
inputThread.start()
# Main loop
while (True):
# Read keyboard inputs
# Note: if this queue were being read in multiple places we would need to use the queueLock above to ensure
# multi-method-call atomic access. Since this is the only place we are removing from the queue, however, in this
# example program, no locks are required.
if (inputQueue.qsize() > 0):
input_str = inputQueue.get()
print("input_str = {}".format(input_str))
if (input_str == EXIT_COMMAND):
print("Exiting serial terminal.")
break # exit the while loop
# Insert your code here to do whatever you want with the input_str.
# The rest of your program goes here.
# Sleep for a short time to prevent this thread from sucking up all of your CPU resources on your PC.
time.sleep(0.01)
print("End.")
# If you run this Python file directly (ex: via `python3 this_filename.py`), do the following:
if (__name__ == '__main__'):
main()
Exemple de sortie:
$ python3 read_keyboard_input.py
Prêt pour la saisie au clavier:
hey
input_str = hey
bonjour
input_str = bonjour
7000
input_str = 7000
exit
input_str = exit
Sortie du terminal série.
Fin.
Références:
- https://pyserial.readthedocs.io/en/latest/pyserial_api.html
- ***** https://www.tutorialspoint.com/python/python_multithreading.htm
- ***** https://en.wikibooks.org/wiki/Python_Programming/Threading
- Python: Comment créer une sous-classe à partir d'une superclasse?
- https://docs.python.org/3/library/queue.html
- https://docs.python.org/3.7/library/threading.html
Liés / croisés:
- Boucle de lecture non bloquante PySerial