Python Flask framework of the project Demo Getting Started

Python + Flask Framework Program Demo Getting Started

　　This example uses a blueprint Flask + + Flask-Login + SQLAlchemy + WTForms + PyMySQL associated schema

Flask Web Framework Introduction

　　Flask micro web framework, the framework itself is very lean, does not mean that function of the weak microcomputer, the core code based Werkzeug, Jinja 2 both libraries, be it in the form of plug-in extensions, and is easy to install and use of plug-ins, and may itself development extensions

Similar to other web frame, flask request (request), the route (route), the response (response) constitute a substantially complete http process.

flask popular main reasons:

1. It has a very complete official documents, very easy to get started
2. There are very good expansion mechanism and the expansion of third-party environment, working in common software has a corresponding expansion of yourself is also very easy to achieve expansion
3. In the form of miniature frame it gives developers greater choice

Introduction blueprint

　　Modular applications can be implemented using Blueprint (Blueprint) in Flask project, a blueprint allows the application level clearer and easier for developers to maintain and develop the project. Blueprint will act on the same request URL address prefix, the request with the same prefix are placed in a module, so find the problem, see a route to quickly find the corresponding view, and solve the problem.

　　Blueprint provides a template filter, static files, templates, and other functions

Flask extensions

Flask-Login库

　　Flask-Login by user session, log on to provide common tasks, such as login (logging in), logout (logging out) and the current user (current user)

　　login_user () function: the user's sign implemented, in the general call sign view function

　　logout_user () function: to achieve logout function

　　current_user property: Gets the current user
　　for the user, if desired page is visible to authorized users, plus @login_required decorator to declare before the appropriate view function, @ login_required decorator for not logged in user access, default processing is redirected to the specified view LoginManager.login_view

 

Flask-Script库

　　Provides insertion of an external script to Flask, including running a server with the development of a custom Python shell, set the script database, cronjobs, and other web applications run outside the command-line tasks; making scripts and systems separately;

　　Flask Flask Script and similar work itself, simply define and add a command from the command line by calling instance Manager;

 

WTForms form

　　WTForms is a support frame form a plurality of web components, mainly used for user authentication data request.

Simple code example:

Myvalidators class (Object): 
    '' 'custom validation rules' '' 
    DEF the __init __ (Self, Message): 
        self.message = Message 
    DEF the __call __ (Self, form, Field): 
        Print (field.data, "information input by the user ") 
        IF field.data ==" Haiyan ": 
            return None 
        The raise validators.ValidationError (self.message) 

class the LoginForm (Form1): 
    '' 'Form1' '' 
    name = simple.StringField ( 
        label =" user name ", 
        the widget widgets.TextInput = (), 
        validators = [ 
            Myvalidators (Message = "user name must be haiyan"), # may be the custom regular  
            validators.DataRequired (message = "user name can not be blank"),
            validators.Length (max = 8, min = 3, message = "Username must be greater than% (max) d and less than% (min) D ") 
        ],
        render_kw = { "class": " form-control"} # set properties 
    ) 

    pwd = simple.PasswordField ( 
        label = "password", 
        validators = [ 
            validators.DataRequired (Message = "password is not blank"), 
            validators.Length ( max = 8, min = 3, message = " password must be longer than% (max) d and less than% (min) D"), 
            validators.Regexp (REGEX = "\ D +", Message = "password must be a number") , 
        ], 
        the widget = widgets.PasswordInput (), 
        render_kw = { "class": "form-Control"} 
    ) 



@ app.route ( '/ Login', Methods = [ "the GET", "the POST"])
        form = LoginForm(formdata=request.form)
        if form.validate(): 
DEF Login ():
    if request.method =="GET":
        form = LoginForm()
        the render_template return ( "the login.html", form = form) 
    the else: 
            Print ( "user-submitted data format used validation value:% S"% form.data) 
            return "login is successful" 
        the else: 
            Print (form.errors , "error message") 
        return render_template ( "login.html", form = form)

　　login.html

<body>
<form action="" method="post" novalidate>
    <p>{{ form.name.label }} {{ form.name }} {{ form.name.errors.0 }}</p>
    <p>{{ form.pwd.label }} {{ form.pwd }} {{ form.pwd.errors.0 }}</p>
    <input type="submit" value="提交">
    <!--用户名：<input type="text">-->
    <!--密码：<input type="password">-->
    <!--<input type="submit" value="提交">-->
</form>
</body>

　　

SQLAlchemy

　　SQLAlchemy is a very powerful relational database framework that supports multiple databases background. SQLAlchemy provides a high-level ORM, also provides the use of native SQL database low-level functions.

　　ORM: the operation will be converted to native SQL objects

　　　　The advantages of
　　　　ease of use, can effectively reduce duplication SQL
　　　　performance loss less
　　　　flexible design, complex queries can easily achieve
　　　　good portability

 

Sample Code

from flask_sqlalchemy import SQLAlchemy

db = SQLAlchemy()


class Student(db.Model):

    s_id = db.Column(db.Integer, primary_key=True, autoincrement=True)
    s_name = db.Column(db.String(16), unique=True)
    s_age = db.Column(db.Integer, default=1)

    __tablename__ = "student"

　　

among them:

S_id type Integer represents the creation of the field of plastic surgery,

primary_key indicates whether the primary key

It indicates that the field is a string String

The only unique indicates that the field

default indicates the default value

autoincrement indicates whether the increment

 

The last code address

github project code Address:  sample project Address

 

Project operating results Screenshot