Flask – SQLite

简述

Python 内置支持SQlite. SQlite3 模块随 Python 发行版一起提供。关于在 Python 中使用 SQLite 数据库的详细教程，请参考此链接。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职能。

第一的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')

HTML 脚本‘student.html’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>

可以看出，表单数据被发布到‘/addrec’绑定的 URLaddrec()功能。

addrec()函数通过以下方式检索表单的数据POST方法并在学生表中插入。插入操作成功或错误对应的消息被渲染到‘result.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()

的 HTML 脚本result.html包含转义语句{{msg}}显示结果Insert手术。


<!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list()所代表的功能‘/list’网址。它填充‘rows’已经有MultiDict包含学生表中所有记录的对象。这个对象被传递给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)

list.html是一个模板，它遍历行集并在 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’它充当应用程序的入口点。


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

这是完整的代码Flask-SQLite应用。


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，并在开发服务器开始运行时运行。访问http://localhost:5000/在显示这样一个简单菜单的浏览器中 -

点击‘Add New Record’打开链接Student Information形式。

填写表格字段并提交。底层函数将记录插入学生表中。

返回首页并点击‘Show List’关联。将显示显示示例数据的表格。