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我目前正在用PyQt中的QSharedMemory和QProcess進行實驗。所以我寫了一個小應用程序來啓動一個進程，它創建一個共享內存段並向其寫入數據。應用程序在輸出寫入數據時讀取數據。父進程無法訪問PyQt中的共享內存
不幸的是，當應用程序嘗試附加到共享內存段時出現此錯誤：QSharedMemory::handle: doesn't exist。看起來父進程不能訪問由子進程分配的着色內存段，除非內存段由父進程分配。
輸出跟蹤：
process state: Starting
process state: Running
process started
process output: Done writing to shared memory
Error accessing shared memory from parent process QSharedMemory::handle: doesn't exist
Error accessing data
process state: Not running
process finished
我的應用程序代碼：
from PyQt4 import QtGui, QtCore
import sys
import pickle
class Widget(QtGui.QWidget):
def __init__(self):
super(Widget,self).__init__()
# create process
self.p = QtCore.QProcess(self)
# Connect to process output
self.p.readyReadStandardOutput.connect(self.on_process_output)
self.p.readyReadStandardError.connect(self.on_process_error_output)
self.p.stateChanged.connect(self.on_process_state_change)
self.p.finished.connect(self.on_process_finished)
self.p.started.connect(self.on_process_started)
self.p.error.connect(self.on_process_error)
self.key = 'share_mem_key'
self.shmem = QtCore.QSharedMemory(self.key)
self.p.start('python.exe shmem_process_test.py "%s"' % self.key)
def on_process_output(self):
s_out = bytes.decode(bytes(self.sender().readAllStandardOutput()))
print 'process output: %s' % (s_out)
if not self.shmem.isAttached() and not self.shmem.attach():
print 'Error accessing shared memory from parent process: %s ' % self.shmem.errorString()
self.shmem.lock()
try:
data = self.shmem.data()
if data:
print pickle.loads(data.asstring())
finally:
print 'Error accessing data'
self.shmem.unlock()
def on_process_error_output(self):
s_out = bytes.decode(bytes(self.sender().readAllStandardError()))
print 'process output: %s' % (s_out)
def on_process_state_change(self,new_state):
states = ["Not running", "Starting", "Running"]
print 'process state: %s' % (states[new_state])
def on_process_finished(self):
print 'process finished'
def on_process_started(self):
print 'process started'
def on_process_error(self):
print 'process error'
# application loop
app = QtGui.QApplication(sys.argv)
widget = Widget()
widget.show()
app.exec_()
我的過程代碼：
from PyQt4 import QtCore
import ctypes
import ctypes.util
import pickle
import sys
CLIB = ctypes.cdll.LoadLibrary(ctypes.util.find_library('c'))
def main(argv):
key = argv[1]
# write to shared memory
data = range(50)
data_bytes = pickle.dumps(data, pickle.HIGHEST_PROTOCOL)
data_len = len(data_bytes)
shmem = QtCore.QSharedMemory(key)
if not shmem.create(data_len):
sys.stderr.write('ERROR: shared memory creation')
sys.stderr.flush()
return
if not shmem.isAttached() and not shmem.attach():
sys.stderr.write('ERROR: shared memory access')
sys.stderr.flush()
return
shmem.lock()
try:
CLIB.memcpy(int(shmem.data()), data_bytes, data_len)
finally:
shmem.unlock()
sys.stdout.write("Done writing to shared memory")
sys.stdout.flush()
if __name__ == '__main__':
main(sys.argv)