我有一个问题：我不知道如何使用会话，结合多线程，高效。那么你可以看到我使用scoped_session。它将透明地创建一个线程本地会话 - 所以它的线程安全。
我的下面和可执行示例有效，只要QTimer的间隔为1000，但如果将值设置为1，则存在一些问题。在GUI站点上，有8个QComboBox() - 对象，我将启动8个线程。在这个例子中，我使用一个表。当我运行此程序时，并非所有QComboBox() - 对象都被填充。有时只有一个QComboBox() - 对象空白或更多。另外，它偶尔发生，我被SQLAlchemy告知连接已关闭。为此，我有一条错误消息：
Traceback (most recent call last):
File "D:\Dan\Python\Xarphus\xarphus\subclass_master_data_load_data_item.py", line 151, in populate_item
self.populate_item_signal.emit(next(self._element))
File "D:\Dan\Python\Xarphus\xarphus\core\manage_data_manipulation_master_data.py", line 232, in select_all
yield record.id, record.relationship
File "D:\Dan\Python\Xarphus\xarphus\core\manage_db_connection.py", line 245, in __exit__
self.session.commit()
File "C:\Python27\lib\site-packages\sqlalchemy\orm\session.py", line 906, in commit
self.transaction.commit()
File "C:\Python27\lib\site-packages\sqlalchemy\orm\session.py", line 465, in commit
t[1].commit()
File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 1632, in commit
self._do_commit()
File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 1663, in _do_commit
self.connection._commit_impl()
File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 726, in _commit_impl
self.connection._reset_agent is self.__transaction:
File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 351, in connection
self._handle_dbapi_exception(e, None, None, None, None)
File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 1405, in _handle_dbapi_exception
util.reraise(*exc_info)
File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 349, in connection
return self._revalidate_connection()
File "C:\Python27\lib\site-packages\sqlalchemy\engine\base.py", line 429, in _revalidate_connection
raise exc.ResourceClosedError("This Connection is closed")
ResourceClosedError: This Connection is closed
而且，如果我多次运行我的程序，我会得到以下消息：
Traceback (most recent call last):
File "C:\Users\Sophus\Desktop\ver_2_simple_problem.py", line 83, in init_object
self._element = self.master_data_manipulation.select_all()
File "C:\Users\Sophus\Desktop\ver_2_simple_problem.py", line 178, in __exit__
self.session.commit()
File "C:\Python27\lib\site-packages\sqlalchemy\orm\session.py", line 906, in commit
self.transaction.commit()
File "C:\Python27\lib\site-packages\sqlalchemy\orm\session.py", line 459, in commit
self._assert_active(prepared_ok=True)
File "C:\Python27\lib\site-packages\sqlalchemy\orm\session.py", line 258, in _assert_active
"This session is in 'committed' state; no further "
sqlalchemy.exc.InvalidRequestError: This session is in 'committed' state; no further SQL can be emitted within this transaction.
这是我的示例代码：有关如何在多个线程中使用SQLAlchemy的更好，更优雅的源代码吗？ Becaouse我不确定这是否正确。
from PyQt4.QtCore import QObject, QThread, pyqtSignal, pyqtSlot, QTimer
from PyQt4.QtGui import QApplication, QPushButton, QVBoxLayout, QDialog, \
QComboBox, QLabel
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import create_engine
from sqlalchemy.exc import SQLAlchemyError
from sqlalchemy.orm import sessionmaker, scoped_session
from sqlalchemy import Table, Column, Integer, String, MetaData
from traceback import format_exc
from sys import exc_info
''' setting up root class for declarative declaration '''
Base = declarative_base()
class PERSON_SALUTATION(Base):
__tablename__ = "person_salutation"
id = Column(Integer, primary_key=True)
salutation = Column(String(50), nullable=False, unique=True)
class MasterDataManipulation(object):
def __init__(self, session_object=None):
self._session_scope = session_object
def select_all(self):
try:
with self._session_scope as session:
for record in session.query(PERSON_SALUTATION):
yield record.id, record.salutation
except AttributeError:
print "select all, desired_trace", format_exc(exc_info())
return
class Worker(QObject):
finish_progress = pyqtSignal()
populate_item_signal = pyqtSignal(object, object)
def __init__(self,
combo_box=None,
query_data=None,
parent=None):
QObject.__init__(self, parent)
self.query_data = query_data
self.combo_box=combo_box
''' Create attributes '''
self._run_semaphore = 1
def init_object(self):
self._element = self.query_data()
self.timer = QTimer()
self.timer.setSingleShot(False)
self.timer.setInterval(1)
self.timer.timeout.connect(self.populate_item)
self.timer.start()
def populate_item(self):
try:
if self._run_semaphore == 0:
self._run_semaphore = 1
raise StopIteration
else:
self.populate_item_signal.emit(next(self._element), self.combo_box)
except StopIteration:
print "StopIteration is raised"
self.timer.stop()
def stop(self):
self._run_semaphore == 0
self.timer.stop()
class SessionScope(object):
def __init__(self, dbms=None, dbdriver=None,
dbuser=None, dbuser_pwd=None,
db_server_host=None, dbport=None, db_name=None,
admin_database=None):
self.dbms = dbms
self.dbdriver = dbdriver
self.dbuser = dbuser
self.dbuser_pwd = dbuser_pwd
self.db_server_host = db_server_host
self.dbport = dbport
self.db_name = db_name
self.admin_database = admin_database
url = '{}+{}://{}:{}@{}:{}/{}'.format(
self.dbms, self.dbdriver, self.dbuser, self.dbuser_pwd, self.db_server_host, self.dbport, self.db_name)
self._Engine = create_engine(url, encoding='utf8', echo=True)
self.session = None
self._session_factory = sessionmaker(bind=self._Engine)
self._Session = scoped_session(sessionmaker(bind=self._Engine, expire_on_commit=False))
''' create tables '''
Base.metadata.create_all(self._Engine)
def __enter__(self):
self.session = self._Session()
return self.session
def __exit__(self, exception, exc_value, traceback):
try:
if exception:
self.session.rollback()
else:
self.session.commit()
finally:
self.session.close()
class MyCustomDialog(QDialog):
finish = pyqtSignal()
def __init__(self, scoped_session=None, parent=None):
QDialog.__init__(self, parent)
self._session_scope = scoped_session
self._list_threads = []
self.init_ui()
self.start_all_selection()
def init_ui(self):
layout = QVBoxLayout(self)
self.combo_person_title = QComboBox(self)
self.combo_person_salutation = QComboBox(self)
self.combo_person_gender = QComboBox(self)
self.combo_person_religion = QComboBox(self)
self.combo_person_relationship_status = QComboBox(self)
self.combo_person_nationality = QComboBox(self)
self.combo_person_eye_color = QComboBox(self)
self.combo_person_hair_color = QComboBox(self)
self.pushButton_populate_combo = QPushButton("Re-populate", self)
self.pushButton_stopp = QPushButton("Stopp", self)
self.pushButton_close = QPushButton("Close", self)
layout.addWidget(self.combo_person_title)
layout.addWidget(self.combo_person_salutation)
layout.addWidget(self.combo_person_gender)
layout.addWidget(self.combo_person_religion)
layout.addWidget(self.combo_person_nationality)
layout.addWidget(self.combo_person_relationship_status)
layout.addWidget(self.combo_person_eye_color)
layout.addWidget(self.combo_person_hair_color)
layout.addWidget(self.pushButton_populate_combo)
layout.addWidget(self.pushButton_stopp)
layout.addWidget(self.pushButton_close)
self.pushButton_stopp.clicked.connect(self.on_finish)
self.pushButton_populate_combo.clicked.connect(self.start_all_selection)
self.pushButton_close.clicked.connect(self.close)
def start_all_selection(self):
list_comboxes = self.findChildren(QComboBox)
for combo_box in list_comboxes:
combo_box.clear()
self.start_thread(combo_box=combo_box)
def fill_combo_boxt(self, item, combo_box):
id, text = item
combo_box.addItem(text)
def on_label(self, i):
self.label.setText("Result: {}".format(i))
def start_thread(self, combo_box=None):
master_data_manipulation = MasterDataManipulation(session_object=self._session_scope)
query_data=master_data_manipulation.select_all
task_thread = QThread(self)
task_thread.work = Worker(query_data=query_data,
combo_box=combo_box,)
''' We need to store threads '''
self._list_threads.append(task_thread)
task_thread.work.moveToThread(task_thread)
task_thread.work.populate_item_signal.connect(self.fill_combo_boxt)
self.finish.connect(task_thread.work.stop)
task_thread.started.connect(task_thread.work.init_object)
task_thread.finished.connect(task_thread.deleteLater)
''' This will emit 'started' and start thread's event loop '''
task_thread.start()
@pyqtSlot()
def abort_workers(self):
self.finish.emit()
for thread in self._list_threads:
''' this will quit **as soon as thread event loop unblocks** '''
thread.quit()
''' so you need to wait for it to *actually* quit'''
thread.wait()
def on_finish(self):
self.finish.emit()
def closeEvent(self, event):
''' Re-implementaate to handle with created threads '''
self.abort_workers()
sys.exit()
def populate_database(sess=None):
try:
with sess as session:
salutations = [PERSON_SALUTATION(salutation="Mister"),
PERSON_SALUTATION(salutation="Miss"),
PERSON_SALUTATION(salutation="Lady"),
PERSON_SALUTATION(salutation="Ma'am"),
PERSON_SALUTATION(salutation="Sir"),
PERSON_SALUTATION(salutation="Queen"),
PERSON_SALUTATION(salutation="Grandma"),]
session.add_all(salutations)
session.commit()
except SQLAlchemyError:
print "SQLAlchemyError", format_exc(exc_info())
def main():
dbms = raw_input('Enter database type: ')
dbdriver = raw_input('Enter database driver: ')
dbuser = raw_input('Enter user name: ')
dbuser_pwd = raw_input('Enter user password: ')
db_server_host = raw_input('Enter server host: ')
dbport = raw_input('Enter port: ')
db_name = raw_input('Enter database name: ')
try:
''' create_engine and scoped_session once per process (per database). '''
session_scope = SessionScope(dbms = dbms,
dbdriver = dbdriver,
dbuser = dbuser,
dbuser_pwd = dbuser_pwd,
db_server_host = db_server_host,
dbport = dbport,
db_name = db_name)
answer = raw_input('Do you want to populate database? Type yes or no: ')
if answer.lower() == 'yes':
populate_database(sess=session_scope)
app = QApplication(sys.argv)
window = MyCustomDialog(scoped_session = session_scope)
window.show()
sys.exit(app.exec_())
except TypeError:
print "ERROR", format_exc(exc_info())
if __name__ == "__main__":
main()