Comment éviter que les programmes Python ne se bloquent lors de la lecture de la sortie du processus ?-Tutoriel Python-php.cn

Comment éviter que les programmes Python ne se bloquent lors de la lecture de la sortie du processus ?

Susan Sarandon

Libérer： 2024-11-02 13:54:29

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How to Avoid Python Programs from Hanging When Reading Process Output?

Arrêter de lire la sortie du processus en Python sans blocage ?

Problème :

Un programme Python doit interagir avec un programme externe processus (par exemple, « top ») qui produit en continu une sortie. Cependant, la simple lecture directe de la sortie peut provoquer le blocage du programme indéfiniment.

Solution :

Pour éviter le blocage, il est essentiel d'utiliser des mécanismes non bloquants ou asynchrones lorsque sortie du processus de lecture. Voici quelques approches possibles :

Fichier temporaire spoolé (recommandé)

Cette méthode utilise un objet fichier dédié pour stocker la sortie du processus.

# ! /usr/bin/env python<br>import subprocess<br>import tempfile<br>import time</p>
<p>def main():</p>
<div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"># Open a temporary file (automatically deleted on closure)
f = tempfile.TemporaryFile()

# Start the process and redirect stdout to the file
p = subprocess.Popen(["top"], stdout=f)

# Wait for a specified duration
time.sleep(2)

# Kill the process
p.terminate()
p.wait()

# Rewind and read the captured output from the file
f.seek(0)
output = f.read()

# Print the output
print(output)
f.close()

Copier après la connexion

Cette approche utilise un thread séparé pour lire en continu la sortie du processus tout en le thread principal poursuit d'autres tâches.

import collections import subprocess import threading import time def read_output(process, append): <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">for line in iter(process.stdout.readline, ""): append(line)

# Start the process and redirect stdout process = subprocess.Popen(["top"], stdout=subprocess.PIPE, close_fds=True) # Create a thread for output reading q = collections.deque(maxlen=200) t = threading.Thread(target=read_output, args=(process, q.append)) t.daemon = True t.start() # Wait for the specified duration time.sleep(2) # Print the saved output print(''.join(q))

importer des collections signal d'importation sous-processus d'importation class Alarm(Exception): <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">pass

# Start the process and redirect stdout process = subprocess.Popen(["top"], stdout=subprocess.PIPE, close_fds=True) # Set signal handler signal.signal(signal.SIGALRM, alarm_handler) signal.alarm(2) try: # Read and save a specified number of lines q = collections.deque(maxlen=200) for line in iter(process.stdout.readline, ""): q.append(line) signal.alarm(0) # Cancel alarm except Alarm: process.terminate() finally: # Print the saved output print(''.join(q))

import collections import subprocess import threading def main(): <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false"># Start the process and redirect stdout process = subprocess.Popen(["top"], stdout=subprocess.PIPE, close_fds=True) # Create a timer for process termination timer = threading.Timer(2, process.terminate) timer.start() # Read and save a specified number of lines q = collections.deque(maxlen=200) for line in iter(process.stdout.readline, ""): q.append(line) timer.cancel() # Print the saved output print(''.join(q))

import collections import subprocess import sys import time def main(): <div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">args = sys.argv[1:] if not args: args = ['top'] # Start the process and redirect stdout process = subprocess.Popen(args, stdout=subprocess.PIPE, close_fds=True) # Save a specified number of lines q = collections.deque(maxlen=200) # Set a timeout duration timeout = 2 now = start = time.time() while (now - start) < timeout: line = process.stdout.readline() if not line: break q.append(line) now = time.time() else: # On timeout process.terminate() # Print the saved output print(''.join(q))