问题：
Python 程序需要与外部交互连续产生输出的过程（例如“顶部”）。但是，直接读取输出可能会导致程序无限期挂起。
解决方案：
为了防止挂起，必须在以下情况下采用非阻塞或异步机制：读取过程输出。以下是一些可能的方法：
此方法利用专用文件对象来存储进程输出。
#! /usr/bin/env python<br>导入子进程<br>导入临时文件<br>导入时间<p>def main():</p><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()
if 名称 == "__main__":
main()
这种方法采用单独的线程来连续读取进程输出，同时主线程继续执行其他任务。
导入集合<br>导入子进程<br>导入线程<br>导入时间</p><p>def read_output(process,append):</p><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)
def main():
# 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))
if 名称 == "__main__":
main()
此方法使用 Unix 信号在指定超时后终止进程，无论是否已读取所有输出。
导入集合<br>导入信号<br>导入子进程</p><p>class Alarm(Exception):</p><div class="code" style="position:relative; padding:0px; margin:0px;"><pre class="brush:php;toolbar:false">pass
def Alarm_handler(signum,frame):
raise Alarm
def main():
# 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))
if 名称 == "__main__":
main()
此方法使用计时器在指定的超时后终止进程。它适用于 Unix 和 Windows 系统。
导入集合<br>导入子进程<br>导入线程</p><p>def main():</p><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))
if name == "__main__":
main()
此方法使用简单的基于时间的循环，用于检查进程输出，如果超过指定超时则将其终止。
导入集合<br>导入子进程<br>导入系统<br>导入时间</p> <p>def main():</p><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))
if 名称 == "__main__":
main()
注意：存储的行数可以根据需要通过设置deque数据结构的'maxlen'参数来调整。
以上是如何避免 Python 程序在读取进程输出时挂起？的详细内容。更多信息请关注PHP中文网其他相关文章！
