1.flask基础

Posted 2021-03-23 pythonblogs

1.flask和django的区别?

flask,是一个轻量级的框架,内置了:路由/视图/模板(jinja2)/cookie/session/中间件.  可扩展强,第三方组件非常多,例如:wtforms/flask-session/flask-sqlalchemy.

django,是一个重武器,django内置了很多功能方便我们使用,例如:admin/orm/模板/form/modelform/session/cookie/中间件/路由/缓存/信号/数据库的读写分离/分页... 

flask,短小精悍可扩展强. 
django,大而全重武器.

django好还是flask好?

小程序,flask比较好.
中大型,django比较好.

2.快速入门

pip3 install flask

2.1 werkzurg

werkzurg是一个wsgi,本质上提供了socket服务端,用于接收用户请求.

django和flask一样,它们内部都没有实现socket服务端,需要依赖wsgi.

• django, wsgiref
• flask, werkzurg

2.1.1 wsgiref实现一个网站

from wsgiref.simple_server import make_server

class WSGIHandler(object):

    def __call__(self,environ, start_response):
        start_response('200 OK', [('Content-Type', 'text/html')])
        return [bytes('<h1>Hello, web!</h1>', encoding='utf-8'), ]


if __name__ == '__main__':
    obj = WSGIHandler()
    httpd = make_server('127.0.0.1', 8000, obj)
    httpd.serve_forever()

2.1.2 werkzeug实现一个网站

from werkzeug.wrappers import Response
from werkzeug.serving import run_simple

class Flask(object):
    def __call__(self,environ, start_response):
        return Response('Hello World!')(environ, start_response)


if __name__ == '__main__':
    app = Flask()
    run_simple('127.0.0.1', 5000, app)

2.2flask程序

from flask import Flask

# 实例化了一个Flask对象
app = Flask(__name__)


# 添加路由关系 
@app.route('/index')
def index():
    return '你好'


if __name__ == '__main__':
    # 启动服务端
    app.run()

3.flask用户登录实例

• 关于返回值

  from flask import Flask,render_template,request,redirect
  
  app = Flask(__name__)
  
  @app.route('/login',methods=['GET','POST'])
  def login():
    return "xxx"
    return render_template('模板文件',参数)
    return redirect(...)
    return jsonify({"k1":123})
  if __name__ == '__main__':
      app.run()

• 关于模板

  默认放在根目录的tempaltes

• 关于用户请求

  request.method
  request.form  # POST
  request.args  # GET

• session

  加密的形式放在用户浏览器的cookie中. 
  from flask import Flask,render_template,request,redirect,jsonify,url_for,session
  
  app.secret_key = "29ualknd872iuknsdgf"
  def auth(func):
      @functools.wraps(func)
      def inner(*args,**kwargs):
          user = session.get('user_info')
          if not user:
              return redirect(url_for('login'))
          return func(*args,**kwargs)
      return inner
  
  @app.route('/login',methods=['GET','POST'])
  def login():
  
      if request.method == 'GET':
          return render_template('login.html')
      user = request.form.get('user')
      pwd = request.form.get('pwd')
      if user == 'alex' and pwd == 'dsb':
          # 在session中存储一个值
          session['user_info'] = user
  
          return redirect(url_for('index'))
      return render_template('login.html',error="用户名或密码错误")

• 在flask视图中添加装饰器

  • 位置route的下面

  • 记得加functools.wraps(...) , 保留函数的元信息.

    from flask import Flask,render_template,request,redirect,jsonify,url_for,session
    
    app.secret_key = "29ualknd872iuknsdgf"
    def auth(func):
        @functools.wraps(func)
        def inner(*args,**kwargs):
            user = session.get('user_info')
            if not user:
                return redirect(url_for('login'))
            return func(*args,**kwargs)
        return inner
    @app.route('/index')
    @auth
    def index():
        user_list = ["庄伯","亮哥",'实验']
        user_info_list = [
            {"name":'庄伯','age':18},
            {"name":'亮哥','age':15},
            {"name":'实验','age':18},
        ]
        return render_template('index.html',user_list=user_list,user_info_list=user_info_list)

• 特殊装饰器:before和after request装饰器

  from flask import Flask,render_template,request,redirect,jsonify,url_for,session
  import functools
  app = Flask(__name__)
  
  app.secret_key = "29ualknd872iuknsdgf"
  
  @app.before_request
  def f1():
      print('f1')
  
  @app.before_request
  def f11():
      print('f11')
  
  
  @app.after_request
  def f2(response):
      print('f2')
      return response
  
  @app.after_request
  def f22(response):
      print('f22')
      return response
  
  
  @app.route('/login')
  def login():
      print('login')
      return 'Login'
  
  @app.route('/index')
  def index():
      print('index')
      return 'index'
  
  
  
  if __name__ == '__main__':
      app.run()
  
  '''
  f1
  f11
  login
  f22
  f2
  '''