一、简单的Flask框架
1）flask简介
Flask 是一个 web 框架。也就是说 Flask 为你提供工具，库和技术来允许你构建一个 web 应用程序。
这个 wdb 应用程序可以使一些 web 页面、博客、wiki、基于 web 的日历应用或商业网站。
Flask 属于微框架（micro-framework）这一类别，微架构通常是很小的不依赖于外部库的框架。
这既有优点也有缺点，优点是框架很轻量，更新时依赖少，并且专注安全方面的 bug，
缺点是，你不得不自己做更多的工作，或通过添加插件增加自己的依赖列表。Flask 的依赖如下：
Werkzeug 一个 WSGI 工具包
jinja2 模板引擎
安装：pip install flask
flask简介
2）最简单的使用flask框架
from flask import Flask
app = Flask(__name__) @app.route("/")
def hello():
return "Hello World!" if __name__ == "__main__":
app.run()
二、Flask框架的组成部分
1）常见的路由系统
@app.route('/user/<username>')
@app.route('/post/<int:post_id>')
@app.route('/post/<float:post_id>')
@app.route('/post/<path:path>')
@app.route('/login', methods=['GET', 'POST'])
所有的路由系统都是基于一下对应关系来处理：
DEFAULT_CONVERTERS = {
'default': UnicodeConverter,
'string': UnicodeConverter,
'any': AnyConverter,
'path': PathConverter,
'int': IntegerConverter,
'float': FloatConverter,
'uuid': UUIDConverter,
}
使用示例
@app.route('/test/<any(about,help,import,class,"foo.bar"):page_name>')
def test(page_name):
return page_name
any使用示例
2）模板使用。
from flask import Flask,render_template,request
# 静态文件和模板路径配置
app = Flask(__name__) def jinxin():
return "<a>活久见</a>" # 设置请求方式
@app.route("/index/",methods=['GET','POST'])
def hello():
# return "Hello World!" # 获取用户请求数据: http://127.0.0.1:5000/index/?k=18
print(request.args) # ImmutableMultiDict([('k', '')]) return render_template('index.html',
k1='root',
k2=[,,],
k3={'name':'user','age':},
k4=jinxin) if __name__ == "__main__":
# IP和端口配置
app.run()
python后端
模板中使用：包含了字符串，列表，字典，以及函数的传值调用
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body>
<h1>index 首页</h1>
<h3>{{k1}}</h3>
<ul>
{% for item in k2 %}
<li>{{item}}</li>
{% endfor %}
</ul> <ul>
{% for k,v in k3.items() %}
<li>{{k}}-{{v}}</li>
{% endfor %}
</ul> {{k4()|safe}}
</body>
</html>
index.html
3）对于Http请求，Flask会讲请求信息封装在request中
request.method
request.args
request.form
request.values
request.files
request.cookies
request.headers
request.path
request.full_path
request.script_root
request.url
request.base_url
request.url_root
request.host_url
request.host
3.1）表单处理示例。request.form
@app.route('/login', methods=['POST', 'GET'])
def login():
error = None
if request.method == 'POST':
if valid_login(request.form['username'],
request.form['password']):
return log_the_user_in(request.form['username'])
else:
error = 'Invalid username/password'
# the code below is executed if the request method
# was GET or the credentials were invalid
return render_template('login.html', error=error)
request.form示例
3.2）上传文件示例。request.files
from flask import request
from werkzeug import secure_filename @app.route('/upload', methods=['GET', 'POST'])
def upload_file():
if request.method == 'POST':
f = request.files['the_file']
f.save('/var/www/uploads/' + secure_filename(f.filename))
...
request.files
3.3）cookies操作示例。request.cookies
from flask import request
@app.route('/setcookie/')
def index():
username = request.cookies.get('username')
# use cookies.get(key) instead of cookies[key] to not get a
# KeyError if the cookie is missing.
from flask import make_response
@app.route('/getcookie')
def index():
resp = make_response(render_template(...))
resp.set_cookie('username', 'the username')
return resp
request.cookies
3.4）用户请求数据。request.args
@app.route("/index/",methods=['GET','POST'])
def hello():
# 获取用户请求数据: http://127.0.0.1:5000/index/?k=18
print(request.args) # ImmutableMultiDict([('k', '')])
return ....
request.args
三、http请求的响应，返回用户的数据。即return的内容
1）返回字符串
@app.route('/index/', methods=['GET', 'POST'])
def index():
return "index"
return "字符串"
2）返回前端模板
from flask import Flask,render_template,request
app = Flask(__name__) @app.route('/index/', methods=['GET', 'POST'])
def index():
return render_template("index.html") app.run()
return render_template("index.html")
3）重定向。跳转
from flask import Flask, redirect, url_for
app = Flask(__name__) @app.route('/index/', methods=['GET', 'POST'])
def index():
# return redirect('/login/')
return redirect(url_for('login')) @app.route('/login/', methods=['GET', 'POST'])
def login():
return "LOGIN" app.run()
return redirect(url_for('login'))
4）指定错误页面
对于找不到路由的指向与404：from flask import Flask, abort
@app.route('/e1/', methods=['GET', 'POST'])
def index():
abort(, 'Nothing')
为404指定前端页面
@app.errorhandler()
def page_not_found(error):
return render_template('page_not_found.html'),
5）使用make_response可以对相应的内容进行操作
from flask import Flask, abort, render_template,make_response
app = Flask(__name__) @app.route('/index/', methods=['GET', 'POST'])
def index():
response = make_response(render_template('index.html'))
# response是flask.wrappers.Response类型
# response.delete_cookie
# response.set_cookie
# response.headers['X-Something'] = 'A value'
return response app.run()
四、session操作.message操作，中间键等
1.1）session操作简介
除请求对象之外，还有一个 session 对象。它允许你在不同请求间存储特定用户的信息。它是在 Cookies 的基础上实现的，
并且对 Cookies 进行密钥签名要使用会话，你需要设置一个密钥。
设置：session['username'] ＝ 'xxx'
删除：session.pop('username', No
1.2）session操作示例
from flask import Flask, session, redirect, url_for, escape, request
app = Flask(__name__)
@app.route('/')
def index():
if 'username' in session:
return 'Logged in as %s' % escape(session['username'])
return 'You are not logged in'
@app.route('/login', methods=['GET', 'POST'])
def login():
if request.method == 'POST':
session['username'] = request.form['username']
return redirect(url_for('index'))
return '''
<form action="" method="post">
<p><input type=text name=username>
<p><input type=submit value=Login>
</form>
'''
@app.route('/logout')
def logout():
# remove the username from the session if it's there
session.pop('username', None)
return redirect(url_for('index'))
# set the secret key. keep this really secret:
app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'
session示例
2）message是一个基于Session实现的用于保存数据的集合，flash方法。其特点是：使用一次就删除
from flask import Flask, flash, redirect, render_template, request app = Flask(__name__)
app.secret_key = 'some_secret' @app.route('/')
def index1():
return render_template('index.html') @app.route('/set')
def index2():
v = request.args.get('p')
flash(v)
return 'ok' if __name__ == "__main__":
app.run()
flash(v)
前端展示
<!DOCTYPE html>
<html>
<head lang="en">
<meta charset="UTF-8">
<title></title>
</head>
<body>
{% with messages = get_flashed_messages() %}
{% if messages %}
<ul class=flashes>
{% for message in messages %}
<li>{{ message }}</li>
{% endfor %}
</ul>
{% endif %}
{% endwith %}
</body>
</html>
index.html
3）自定义中间键。environ, start_response
自定义中间件
from flask import Flask,render_template,request,make_response,redirect,url_for,session
app = Flask(__name__)
@app.route("/index/",methods=['GET','POST'])
def hello():
print('在路由中')
return 'OK'
class Foo:
def __init__(self,w):
self.w = w
def __call__(self, environ, start_response):
print("进入路由之前")
obj = self.w(environ, start_response)
print("进入路由之后")
return obj
if __name__ == "__main__":
# app.wsgi_app = my_wsgi_app
# . 自定制中间件
app.wsgi_app = Foo(app.wsgi_app)
app.run()
自定义中间键
标准写法改良
from flask import Flask, flash, redirect, render_template, request app = Flask(__name__)
app.secret_key = 'some_secret' @app.route('/')
def index1():
return render_template('index.html') @app.route('/set')
def index2():
v = request.args.get('p')
flash(v)
return 'ok' class MiddleWare:
def __init__(self,wsgi_app):
self.wsgi_app = wsgi_app def __call__(self, *args, **kwargs): return self.wsgi_app(*args, **kwargs) if __name__ == "__main__":
app.wsgi_app = MiddleWare(app.wsgi_app)
app.run(port=)
MiddleWare中间键