PyQT QTableView实现数据库增删改查(CRUD)操作的可视化
PyQT 提供了模型/视图 (Model/View)编程模式 并提供了相应的实现类 QTableView 与QSqlTableModel，以可视化的方式对数据库进行操作。
可以理解为：
Model层从View层分离出来，Model层负责直接操作数据库。 View视图层负责显示数据，以及管理业务逻辑。 同时还提供了delegate类用于渲染单元格
本文将实现1个Model/View架构的实例，实现对数据库的增删改查。
下面用实例来演示这一实现过程。
1、准备测试数据库
为了方便，提供如下脚本创建数据库，并插入测试记录
# 用于向数据库表插入数据
import sys
from PyQt5.QtSql import *
# Create the connection
con = QSqlDatabase.addDatabase("QSQLITE")
con.setDatabaseName("./contacts.sqlite")
# Open the connection
if not con.open():
print("Database Error: %s" % con.lastError().databaseText())
sys.exit(1)
# Create a query and execute it right away using .exec()
createTableQuery = QSqlQuery()
createTableQuery.exec(
"""
CREATE TABLE contacts (
id INTEGER PRIMARY KEY AUTOINCREMENT UNIQUE NOT NULL,
name VARCHAR(40) NOT NULL,
job VARCHAR(50),
email VARCHAR(40) NOT NULL
)
"""
)
print(con.tables())
# Creating a query for later execution using .prepare()
insertDataQuery = QSqlQuery()
insertDataQuery.prepare(
"""
INSERT INTO contacts (
name,
job,
email
)
VALUES (?, ?, ?)
"""
)
# Sample data， you can replace data with yours
data = [
("王小乙", "Senior Web Developer", "[email protected]"),
("Lara", "Project Manager", "[email protected]"),
("David", "Data Analyst", "[email protected]"),
("Jane", "Senior Python Developer", "[email protected]"),
]
# Use .addBindValue() to insert data
for name, job, email in data:
insertDataQuery.addBindValue(name)
insertDataQuery.addBindValue(job)
insertDataQuery.addBindValue(email)
insertDataQuery.exec()
query = QSqlQuery()
query.exec("select * from contacts")
while query.next():
print(query.value(0), query.value(1), query.value(2))
print(query.finish())
con.close()
2、创建model对象，并连接至数据库
PyQT提供了QSqlDatabase类负责数据库连接，其封闭了多种数据库连接API, 所以推荐使用。
与 QAbstractTableModel 比较，你不需要实现繁琐的data()方法等，QSqlDatabase已经帮我们封装好了，开箱即用。
mydb = QSqlDatabase.addDatabase("QSQLITE")
mydb.setDatabaseName('./contacts.sqlite') #设置数据名称
mydb.open()
self.model= QSqlTableModel(None,mydb)
# self.model.database() 也会返回QSqlDatabase对象
self.model.setTable(‘contacts’) # 设置相关表
数据也可以是MySql, PostGreSQL 等, 如下，需要设置更多的参数，
db = QSqlDatabase.addDatabase("QMYSQL")
db.setHostName("localhost")
db.setDatabaseName("customdb")
db.setUserName("root")
db.setPassword("123456")
db.open()
按面向对象的方式，创建1个ContactsModel类，并提供添加，删除，查询等方法
# 文件名： mv_contact_db_model.py
from PyQt5.QtCore import Qt
from PyQt5.QtSql import *
from PyQt5.QtWidgets import QMessageBox
class ContactsModel:
def __init__(self):
"""Create and set up the model."""
mydb = QSqlDatabase.addDatabase("QSQLITE")
mydb.setDatabaseName('./contacts.sqlite')
if not mydb.open():
QMessageBox.critical(
None,
"QTableModel Example - Error!",
"Database Error: %s" % mydb.lastError().databaseText(),
)
self.model = QSqlTableModel(None, mydb)
self.model.setTable("contacts") # 选择表名
self.model.setEditStrategy(QSqlTableModel.OnFieldChange)
self.model.select() # 相当于执行select语句，把数据读入model
headers = ("ID", "姓名", "工作岗位", "邮箱")
for columnIndex, header in enumerate(headers):
self.model.setHeaderData(columnIndex, Qt.Horizontal, header)
def addContact(self, data):
"""Add a contact to the database."""
rows = self.model.rowCount()
self.model.insertRows(rows, 1)
for column, field in enumerate(data):
self.model.setData(self.model.index(rows, column + 1), field)
self.model.submitAll()
self.model.select()
def deleteContact(self, row):
"""Remove a contact from the database."""
self.model.removeRow(row)
self.model.submitAll()
self.model.select()
def queryContact(self,condition):
""" query contacts with condition to name field"""
self.model.setFilter(condition)
self.model.select()
3. QTableView 绑定 Model ，提供可视化界面
QTableView通过 setModel()方法绑定 model.
self.view = QTableView()
self.view.setModel(self.ContactsModel.model)
本例的主窗口布局，除了TableView，还提供了添加、删除记录的按钮，查询条件输入框等。
单击添加记录按钮后，会弹出1个新记录输入对话框。
下面是实现的完整代码。
# 文件名: mv_contact.py
import sys
from PyQt5.QtCore import Qt
from PyQt5.QtSql import QSqlDatabase, QSqlTableModel
from PyQt5.QtWidgets import *
from mv_contact_db_model import ContactsModel
class AddDialog(QDialog):
"""Add Contact dialog."""
def __init__(self, parent=None):
"""Initializer."""
super().__init__(parent=parent)
self.setWindowTitle("Add Contact")
self.vbox = QVBoxLayout()
self.setLayout(self.vbox)
self.data = None
self.setupUI()
def setupUI(self):
"""Setup the Add Contact dialog's GUI."""
# Create line edits for data fields
self.nameField = QLineEdit()
self.nameField.setObjectName("Name")
self.jobField = QLineEdit()
self.jobField.setObjectName("Job")
self.emailField = QLineEdit()
self.emailField.setObjectName("Email")
# Lay out the data fields
layout = QFormLayout()
layout.addRow("Name:", self.nameField)
layout.addRow("Job:", self.jobField)
layout.addRow("Email:", self.emailField)
self.vbox.addLayout(layout)
# Add standard buttons to the dialog and connect them
self.buttonsBox = QDialogButtonBox(self)
self.buttonsBox.setOrientation(Qt.Horizontal)
self.buttonsBox.setStandardButtons(
QDialogButtonBox.Ok | QDialogButtonBox.Cancel
)
self.buttonsBox.accepted.connect(self.accept)
self.buttonsBox.rejected.connect(self.reject)
self.vbox.addWidget(self.buttonsBox)
def accept(self):
"""Accept the data provided through the dialog."""
self.data = []
for field in (self.nameField, self.jobField, self.emailField):
if not field.text():
QMessageBox.critical(
self,
"Error!",
f"You must provide a contact's {field.objectName()}",
)
self.data = None # Reset .data
return
self.data.append(field.text())
if not self.data:
return
super().accept()
class MyWin(QMainWindow):
def __init__(self, parent=None):
super(MyWin,self).__init__()
self.setWindowTitle("QTableView Example")
self.resize(800, 400)
# Set up the model
self.ContactsModel = ContactsModel()
# Set up the view
self.view = QTableView()
self.view.setModel(self.ContactsModel.model)
self.view.resizeColumnsToContents()
self.view.setSelectionBehavior(QAbstractItemView.SelectRows)
# Create buttons
self.addButton = QPushButton("添加记录")
self.addButton.clicked.connect(self.openAddDialog)
self.deleteButton = QPushButton("删除记录")
self.deleteButton.clicked.connect(self.deleteContact)
self.clearAllButton = QPushButton("删除所有")
self.clearAllButton.clicked.connect(self.deleteAll)
# Search
self.formlayout = QFormLayout(self)
self.qry_input_name = QLineEdit()
self.qry_input_name.setMaximumWidth(120)
self.button_search = QPushButton("查询",self)
self.button_search.setCheckable(True)
self.button_search.clicked.connect(self.queryContact)
# 布局
self.mywidget = QWidget()
self.setCentralWidget(self.mywidget)
hbox = QHBoxLayout(self.mywidget)
vbox = QVBoxLayout(self.mywidget)
vbox.addWidget(self.addButton)
vbox.addWidget(self.deleteButton)
vbox.addWidget(QLabel("姓名"))
vbox.addWidget(self.qry_input_name)
# vbox.addLayout(self.formlayout)
vbox.addWidget(self.button_search)
vbox.addStretch()
vbox.addWidget(self.clearAllButton)
hbox.addWidget(self.view)
hbox.addLayout(vbox)
self.mywidget.setLayout(hbox)
def openAddDialog(self):
"""Open the Add Contact dialog."""
dialog = AddDialog(self)
if dialog.exec() == QDialog.Accepted:
self.ContactsModel.addContact(dialog.data)
self.view.resizeColumnsToContents()
def deleteContact(self):
"""Delete the selected contact from the database."""
row = self.view.currentIndex().row()
if row < 0:
return
messageBox = QMessageBox.warning(
self,
"Warning!",
"Do you want to remove the selected contact?",
QMessageBox.Ok | QMessageBox.Cancel,
)
if messageBox == QMessageBox.Ok:
self.ContactsModel.deleteContact(row)
def deleteAll(self):
"""delete all records in the contacts table"""
QMessageBox.warning(
self,
"Info!",
"暂时不支持清除全部记录",
QMessageBox.Ok,
)
def queryContact(self,checked):
"""Prepare query condition, call query method of ContactsModel"""
print("checled status: ",checked)
if checked:
self.button_search.setText("取消查询")
input = self.qry_input_name.text()
query = f"name like '%{input}%'"
else:
query = f"name like '%%'"
self.button_search.setText("查询")
self.qry_input_name.setText('')
# call ContactsModel's query method
self.ContactsModel.queryContact(query)
app = QApplication(sys.argv)
win = MyWin()
win.show()
sys.exit(app.exec_())
4. 可视化显示有外键的数据库表
如下表, city， country两字段是foreign key字段，QSqlTableModel 对外键表默认只提供 id 字段 
如何显示成如格式，也就是显示外键表的名字而不是id
使用 QSqlRelationalTableModel模型类， 用setRelation()方法来建立表间关系
mode = QSqlRelationalTableModel()
model.setTable("employee")
model.setRelation(2, QSqlRelation("city", "id", "name"))
model.setRelation(3, QSqlRelation("country", "id", "name"))
model.setRelation(2, QSqlRelation("city", "id", "name"))
表示第2列是foreign key, 使用city 表， 显示内容由 city.id更换为city.name。
接下来，如果需要编辑外键字段，即将city, country列变成下拉列表，从外键表中选择已存在的值，如何实现呢？
在该单元格使用QSqlRelationalDelegate 类。 实现代码如下：
view = QTableView()
view.setModel(model)
view.setItemDelegate(QSqlRelationalDelegate(view))
显示结果如下：
总结
使用 QTableView 以及 QSqlDatabase 可视化访问数据库，这两个类帮助开发者隐藏很多细节，使用简单，开发效率高。
如果需要对外观进行美化，可以采用delegate进行渲染单元格，用stylesheet来渲染QT窗口与控件。