Python Learning Notes (4)---Introduction to flask development

First give the Flask Chinese document address: http://docs.jinkan.org/docs/flask/

1 Web Development Basics:

Front-end development:

• Html

• Css

• Javascript

MVC design Pattern:

• View

• Controller

• Model

http

• Based on the request corresponding mode

• No status

• Request method: GET, POST, Delete,put

Basic components of the flask application:

# Coding=utf-8from Flask Import Flask # import Class app = Flask (__name__) # Instantiate Flask instance @app.route ('/') # The routing portion of the app, given the following view function Urldef Hello_world (): Return ' Hello world! ' if __name__ = = ' __main__ ': # Run App.run ()

Routing and Reverse routing flaskapp.py:

# coding=utf-8from flask import flask, request, url_for  #  Import class App  = flask (__name__)   #  Instantiate Flask instance @app.route ('/')   #  the routing portion of the app, For the following view function give Urldef hello_world ():    return  ' hello world! ' @app. Route ('/user/<id> ')    # , methods=[' POST ') def hello_user (ID):     return  ' hello user! '  + id@app.route ('/query_user ')   #  access:http://127.0.0.1:5000/query_user?id=2def  Query_user ():     id = request.args.get (' id ')     return  ' Query_user '  + id#  reverse route @app.route ('/query_url ')   # http://127.0.0.1:5000/query_ url  shown as: Query url/query_userdef query_url ():    return  ' Query url '  + url_for (' query_user ') if __name__ ==  ' __main__ ':  #  run &NBSP;&NBSp;  app.run () 

Flash templates:

Find Jinja2 a python template engine: Https://github.com/mitsuhiko

Visit http://jinja.pocoo.org/

Flack Rendering:

To create a index.html file:

<! DOCTYPE html>

Add in flaskapp.py:
@app. Route ('/') # The routing portion of the app, given Urldef Hello_world () for the following view function: content = "Hello World" return render_template ("index.htm L ", content=content)

If a complex object is passed in:
models.py
Class User (object): Def __init__ (self, user_id, user_name): self.user_id = user_id Self.user_name = user_ Name
User_index.html:
<! DOCTYPE html>

To set up a route:
@app. Route ('/user ') def user_index (): User = User (1, ' Thystar ') return render_template ("user_index.html", User=user)


Conditional statements in a template:
def q_user (user_id): User = None if int (user_id) = = 1:user = User (1, ' Thystar ') return render_template ("U Ser_id.html ", User=user)
User_id.html
<! DOCTYPE html>

Exception handling:
@app. ErrorHandler (404) def not_found (e): Return render_template ("404.html")

404.HTML:
<! DOCTYPE html>

Another way is:
@app. Route ('/user/<id> ') #, methods=[' POST ') def hello_user (ID): if int (id) = = 1:return Render_templat E ("index.html") Else:abort (404)


Finally, mention the inheritance of the template:
In some cases, when a Web page is toggled, some pages do not change, such as the navigation bar, so in order to avoid code duplication, use inheritance: Invariant parts are implemented in the parent class, and the changed parts are implemented in subclasses
First, define the base class Base.html:
<! DOCTYPE html>

Then define two subclasses of ont_base.html and two_base.html
<!--inheriting base class-->{% extends "base.html"%}{% block content%} 
<!--inheriting base class-->{% extends "base.html"%}{% block content%} 

Add in flaskapp.py:
@app. Route ('/one ') def one_base (): Return Render_template ("one_base.html") @app. Route ('/two ') def two_base (): Return re Nder_template ("two_base.html")

Open Browser test: Http://127.0.0.1:5000/two



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Python Learning Notes (4)---Introduction to flask development