PyQt 应用程序与 sqlalchemy 数据库

Question

我尝试创建一个 PyQt 应用程序，数据存储在数据库中。我想使用 sqlachemy 访问我的数据并使用 PyQt 中的模型显示数据。

在这个例子中，我使用了组合框来显示我的数据。

我的代码 "works" 很糟糕，因为每次我单击组合框时模型都会检查数据库数千次，使其非常缓慢。

这样做的 "canonical method" 是什么？

我在 Windows 下使用 Python 3.4 和 PyQt 4。我的Python-Sqlalchemy-PyQt-english水平很低

#!/usr/bin/env python3
# -*- coding: utf-8 -*- 

import sys
import sqlalchemy
from sqlalchemy.ext.declarative import declarative_base

from PyQt4 import QtCore, QtGui, uic

# My base structure

base = declarative_base()

class User(base):
    __tablename__ = "users"
    id_ = sqlalchemy.Column(sqlalchemy.Integer, primary_key=True)

    name = sqlalchemy.Column(sqlalchemy.String(20))

    def __repr__(self):
        return "<User(id='%s', name='%s')>" % (self.id_, self.name)

# Creating my base and my session
engine = sqlalchemy.create_engine("sqlite:///my_db.db")
base.metadata.create_all(engine)

DBsession = sqlalchemy.orm.sessionmaker(bind=engine)
session = DBsession()

# My model, i just want to show data
class UserListModel(QtCore.QAbstractListModel):

    def __init__(self, session, parent = None):
        QtCore.QAbstractListModel.__init__(self, parent)
        self.session = session

    def rowCount(self, parent):
        return len(get_users(self.session))

    def data(self, index, role):
        users = get_users(self.session)

        # Only for debug
        print(users)

        if role == QtCore.Qt.DisplayRole:
            value = users[index.row()]
            return "%s : %s" % (value.id_, value.name)

def add_user(session, tmp_name):
    session.add(User(name=tmp_name))
    session.commit()

def get_users(session):
    users = session.query(User).all()
    return users

# Populating my db
session.add(User(name="edouard"))
session.add(User(name="jean"))
session.add(User(name="albert"))
session.commit()

# Creating my app
app = QtGui.QApplication(sys.argv)
mywindow = QtGui.QWidget()

# Combobox and his model
combobox = QtGui.QComboBox(mywindow)
combobox.setModel(UserListModel(session))

mywindow.show()
sys.exit(app.exec_())

Answer 1

我对您的代码做了一些改进，但我对 PyQt 不熟悉，所以我相信这可以进一步改进。不管怎样，经常调用数据库的原因之一是，只要 PyQt 想要重绘列表，就会调用 UserListModel.data()。这发生在例如组合框内的鼠标移动，所以我们真的不想每次调用 data().

时都访问数据库

通过填充__init__()中的用户列表，我们缓存数据库结果，避免频繁查询。这只会带您走这么远，因为您还必须在修改数据库内容时更新此缓存。所以在添加或删除用户时，还需要调用UserListModel.refresh().

#!/usr/bin/env python3
# -*- coding: utf-8 -*- 

import sys
import sqlalchemy
from sqlalchemy.ext.declarative import declarative_base

from PyQt4 import QtCore, QtGui, uic

# My base structure

base = declarative_base()

class User(base):
    __tablename__ = "users"
    id_ = sqlalchemy.Column(sqlalchemy.Integer, primary_key=True)

    name = sqlalchemy.Column(sqlalchemy.String(20))

    def __repr__(self):
        return "<User(id='%s', name='%s')>" % (self.id_, self.name)

# Creating my base and my session
engine = sqlalchemy.create_engine("sqlite:///my_db.db", echo='debug')
base.metadata.create_all(engine)

DBsession = sqlalchemy.orm.sessionmaker(bind=engine)
session = DBsession()

# My model, i just want to show data
class UserListModel(QtCore.QAbstractListModel):

    def __init__(self, session, parent = None):
        QtCore.QAbstractListModel.__init__(self, parent)
        self.session = session
        self.refresh()

    def refresh(self):
        self.users = self.session.query(User).all()

    def rowCount(self, parent):
        return len(self.users)

    def data(self, index, role):
        if role == QtCore.Qt.DisplayRole:
            value = self.users[index.row()]
            return "%s : %s" % (value.id_, value.name)

def add_user(session, tmp_name):
    session.add(User(name=tmp_name))
    session.commit()

# Populating my db
if not session.query(User).count():
    session.add(User(name="edouard"))
    session.add(User(name="jean"))
    session.add(User(name="albert"))
    session.commit()

# Creating my app
app = QtGui.QApplication(sys.argv)
mywindow = QtGui.QWidget()

# Combobox and his model
combobox = QtGui.QComboBox(mywindow)
combobox.setModel(UserListModel(session))

mywindow.show()
sys.exit(app.exec_())

PyQt 应用程序与 sqlalchemy 数据库

PyQt application with sqlalchemy database

python

sqlalchemy

pyqt

pyqt4