Flask 简明教程

Flask – SQLite

Python对 SQlite 有内置支持。Python发行版附带了SQlite3模块。有关在Python中使用SQLite数据库的详细教程，请参阅 this link 。在本节中，我们将看到Flask应用程序如何与SQLite交互。

创建SQLite数据库 ‘database.db’ 并在其中创建一个学生的表。

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()

我们的Flask应用程序有三个 View 函数。

第一个 new_student() 函数绑定到URL规则 (‘/addnew’) 。它呈现一个包含学生信息表单的HTML文件。

@app.route('/enternew')
def new_student():
   return render_template('student.html')

‘student.html’ 的HTML脚本如下 −

<html>
   <body>
      <form action = "{{ url_for('addrec') }}" method = "POST">
         <h3>Student Information</h3>
         Name<br>
         <input type = "text" name = "nm" /></br>

         Address<br>
         <textarea name = "add" ></textarea><br>

         City<br>
         <input type = "text" name = "city" /><br>

         PINCODE<br>
         <input type = "text" name = "pin" /><br>
         <input type = "submit" value = "submit" /><br>
      </form>
   </body>
</html>

如您所见，表单数据发布到绑定 addrec() 函数的 ‘/addrec’ URL。

此 addrec() 函数通过 POST 方法检索表单数据并插入 students 表中。插入操作成功或失败的对应消息呈现在 ‘result.html’ 上。

@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 脚本包含转义语句 {{msg}} ，它显示 Insert 操作的结果。

<!doctype html>
<html>
   <body>
      result of addition : {{ msg }}
      <h2><a href = "\">go back to home page</a></h2>
   </body>
</html>

该应用程序包含另一个由 ‘/list’ URL 表示的 list() 函数。它将 ‘rows’ 填充成一个 MultiDict 对象，其中包含 students 表中的所有记录。该对象传递给 list.html 模板。

@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)

此 list.html 是一个模板，它对行集进行迭代并在 HTML 表中呈现数据。

<!doctype html>
<html>
   <body>
      <table border = 1>
         <thead>
            <td>Name</td>
            <td>Address>/td<
            <td>city</td>
            <td>Pincode</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 = "/">Go back to home page</a>
   </body>
</html>

最后， ‘/’ URL 规则呈现一个 ‘home.html’ ，作为应用程序的入口点。

@app.route('/')
def home():
   return render_template('home.html')

以下为 Flask-SQLite 应用程序的完整代码。

from flask import Flask, render_template, request
import sqlite3 as sql
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)

if __name__ == '__main__':
   app.run(debug = True)

从 Python Shell 运行此脚本并作为开发服务器开始运行。在浏览器中访问 http://localhost:5000/ ，它会显示类似这样的简单菜单 -

simple menu

点击 ‘Add New Record’ 链接以打开 Student Information 表单。

adding new record

填写表单字段并提交。底层函数会将记录插入 students 表。

record successfully added

返回主页并点击 ‘Show List’ 链接。程序会显示包含示例数据的表格。

table showing sample data