Flask之Hello world 详解

**Flask之Hello world 详解

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以下讲解假设你对python有基本了解,熟悉wsgi,以及了解某种python web framework.

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello_world():
    return "HELLO WROLD"

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

Flask的实例app就是我们的WSGI application.
创建Flask实例需要指定一个参数,这个参数一般是application的模块名字或者是包名.Flask根据这个参数定位templates,static files等.
route装饰器告诉Flask什么样的请求路径对应这个函数

####Routing

route()装饰器支持变量规则,用<variable_name>表示.还可以制订一个转换器.例如:

@app.route('/user/<username>')
def show_user_profile(username):
    # show the user profile for that user
    return 'User %s' % username

@app.route('/post/<int:post_id>')
def show_post(post_id):
    # show the post with the given id, the id is an integer
    return 'Post %d' % post_id

@app.route('/user/<path:location>')
def show_path(location):
    return location

有三种转换器:

int	    accepts integers
float	like int but for floating point values
path	like the default but also accepts slashes

####HTTP METHOD

from flask import request

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == "POST":
        return 'post'
    else:
        return 'get'

####Static Files

在package或则module同目录下创建static目录

url_for('static', filename='style.css')

####rendering templates

默认Flask配置JinJia2作为模板引擎,因为他们是一家的.Flask会在templates目录下查找模板文件,如果application是一个module,那么这个templates目录与application同级目录.如果他是一个package:

case 1: a module:

/application.py

/templates

/hello.html
case 2: a application

/application

/init .py

/templates

/hello.html

渲染模板使用render_template()

from flask import render_template
@app.route('/hello/')
@app.route('/hello/<name>')
def hello(name=None):
    return render_template('hello.html',name=name)

JinJia2 模板的语法和Mako以及django的语法都差不多,可以稍作了解

<!doctype html>
<title>Hello from Flask</title>
{% if name %}
  <h1>Hello {{ name }}!</h1>
{% else %}
  <h1>Hello World!</h1>
{% endif %}

####Context locals

先跳过