Flask 教程
Flask SQLite
Python拥有对SQlite的内置支持。 SQlite3模块随附Python发行版。在本节中，我们将看到Flask应用程序如何与SQLite进行交互。
创建一个SQLite数据库 ‘database.db’并在其中创建一个student表。
# Filename : example.py
# Copyright : 2020 By Nhooo
# Author by : www.nhooo.com
# Date : 2020-08-08
import sqlite3
conn = sqlite3.connect('database.db')
print "Opened database successfully";
conn.execute('CREATE TABLE students (name TEXT, addr TEXT, city TEXT, pin TEXT)')
print "Table created successfully";
conn.close()Flask应用程序有三个视图函数。
第一个new_student()函数绑定到URL规则(‘/addnew’)。 它呈现包含学生信息表单的HTML文件。
# Filename : example.py
# Copyright : 2020 By Nhooo
# Author by : www.nhooo.com
# Date : 2020-08-08
@app.route('/enternew')
def new_student():
return render_template('student.html')‘student.html’的HTML脚本如下 -
# Filename : example.py
# Copyright : 2020 By Nhooo
# Author by : www.nhooo.com
# Date : 2020-08-08
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Flask示例</title>
</head>
<body>
<form action = "{{ url_for('addrec') }}" method = "POST">
<h3>学生信息</h3>
姓名<br>
<input type = "text" name = "nm" /></br>
地址<br>
<textarea name = "add" /><br>
城市<br>
<input type = "text" name = "city" /><br>
邮编<br>
<input type = "text" name = "pin" /><br>
<input type = "submit" value = "提交" /><br>
</form>
</body>
</html>可以看出，表单数据发布到绑定addrec()函数，对应于URL => ‘/addrec’ 。
这个addrec()函数通过POST方法检索表单的数据并插入到学生表中。 与插入操作中的成功或错误相对应的消息呈现为’result.html’。
# Filename : example.py
# Copyright : 2020 By Nhooo
# Author by : www.nhooo.com
# Date : 2020-08-08
@app.route('/addrec',methods = ['POST', 'GET'])
def addrec():
if request.method == 'POST':
try:
nm = request.form['nm']
addr = request.form['add']
city = request.form['city']
pin = request.form['pin']
with sql.connect("database.db") as con:
cur = con.cursor()
cur.execute("INSERT INTO students (name,addr,city,pin)
VALUES (?,?,?,?)",(nm,addr,city,pin) )
con.commit()
msg = "Record successfully added"
except:
con.rollback()
msg = "error in insert operation"
finally:
return render_template("result.html",msg = msg)
con.close()result.html 的HTML脚本包含显示插入操作结果的转义语句{{msg}}。
# Filename : example.py
# Copyright : 2020 By Nhooo
# Author by : www.nhooo.com
# Date : 2020-08-08
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Flask示例</title>
</head>
<body>
操作结果 : {{ msg }}
<h2><a href = "/">返回主页</a></h2>
</body>
</html>该应用程序包含由URL => ‘/list’表示的另一个list()函数。 它将“行”填充为包含学生表中所有记录的MultiDict对象。 这个对象传递到 list.html 模板。
# Filename : example.py
# Copyright : 2020 By Nhooo
# Author by : www.nhooo.com
# Date : 2020-08-08
@app.route('/list')
def list():
con = sql.connect("database.db")
con.row_factory = sql.Row
cur = con.cursor()
cur.execute("select * from students")
rows = cur.fetchall();
return render_template("list.html",rows = rows)这个list.html是一个模板，它遍历行集合并在HTML表格中呈现数据。
# Filename : example.py
# Copyright : 2020 By Nhooo
# Author by : www.nhooo.com
# Date : 2020-08-08
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>Flask示例</title>
</head>
<body>
<table border = 1>
<thead>
<td>改名</td>
<td>地址</td>
<td>城市</td>
<td>编码</td>
</thead>
{% for row in rows %}
<tr>
<td>{{row["name"]}}</td>
<td>{{row["addr"]}}</td>
<td>{{row["city"]}}</td>
<td>{{row['pin']}}</td>
</tr>
{% endfor %}
</table>
<a href = "/">返回主页</a>
</body>
</html>最后，URL => ‘/‘规则呈现一个’home.html’作为应用程序的入口点。
# Filename : example.py
# Copyright : 2020 By Nhooo
# Author by : www.nhooo.com
# Date : 2020-08-08
@app.route('/')
def home():
return render_template('home.html')这里是Flask-SQLite应用程序的完整代码。
# Filename : example.py
# Copyright : 2020 By Nhooo
# Author by : www.nhooo.com
# Date : 2020-08-08
from flask import Flask, render_template, request
import sqlite3 as sql
import sqlite3
app = Flask(__name__)
@app.route('/')
def home():
return render_template('home.html')
@app.route('/enternew')
def new_student():
return render_template('student.html')
@app.route('/addrec',methods = ['POST', 'GET'])
def addrec():
if request.method == 'POST':
try:
nm = request.form['nm']
addr = request.form['add']
city = request.form['city']
pin = request.form['pin']
with sql.connect("database.db") as con:
cur = con.cursor()
cur.execute("INSERT INTO students (name,addr,city,pin) VALUES (?,?,?,?)",(nm,addr,city,pin) )
con.commit()
msg = "Record successfully added"
except:
con.rollback()
msg = "error in insert operation"
finally:
return render_template("result.html",msg = msg)
con.close()
@app.route('/list')
def list():
con = sql.connect("database.db")
con.row_factory = sql.Row
cur = con.cursor()
cur.execute("select * from students")
rows = cur.fetchall();
return render_template("list.html",rows = rows)
@app.route('/init')
def init():
conn = sqlite3.connect('database.db')
print ("Opened database successfully")
conn.execute('CREATE TABLE students (name TEXT, addr TEXT, city TEXT, pin TEXT)')
print ("Table created successfully")
conn.close()
return None
if __name__ == '__main__':
app.run(debug = True)从Python shell运行此脚本，并在开发服务器开始运行时运行。 访问:http:// localhost:5000/ 在浏览器中显示一个这样的简单菜单 - 
点击 “添加学生信息” 链接打开添加学生信息表单。 
填写表单并提交。底层函数将该记录插入到学生表中。
返回主页并点击“显示列表”链接，将显示样本数据的表格。 