Flask是一个基于Python开发并且依赖 jinja2 模板和 Werkzeug WSGI 服务的一个微型框架，对于Werkzeug本质是Socket服务端，其用于接收http请求并对请求进行预处理，然后触发Flask框架，开发人员基于Flask框架提供的功能对请求进行相应的处理，并返回给用户，如果要返回给用户复杂的内容时，需要借助jinja2模板来实现对模板的处理，即：将模板和数据进行渲染，将渲染后的字符串返回给用户浏览器。

“微”(micro) 并不表示你需要把整个 Web 应用塞进单个 Python 文件（虽然确实可以 ），也不意味着 Flask 在功能上有所欠缺。微框架中的“微”意味着 Flask 旨在保持核心简单而易于扩展。Flask 不会替你做出太多决策——比如使用何种数据库。而那些 Flask 所选择的——比如使用何种模板引擎——则很容易替换。除此之外的一切都由可由你掌握。如此，Flask 可以与您珠联璧合。

默认情况下，Flask 不包含数据库抽象层、表单验证，或是其它任何已有多种库可以胜任的功能。然而，Flask 支持用扩展来给应用添加这些功能，如同是 Flask 本身实现的一样。众多的扩展提供了数据库集成、表单验证、上传处理、各种各样的开放认证技术等功能。Flask 也许是“微小”的，但它已准备好在需求繁杂的生产环境中投入使用。

pip3 install flask

一. 基本使用

from flask import Flaskapp = Flask(__name__)@app.route('/')
def hello_world():return 'Hello World!'if __name__ == '__main__':app.run()

二、配置文件

flask中的配置文件是一个flask.config.Config对象（继承字典）,默认配置为：{'DEBUG':                                get_debug_flag(default=False),  # 是否开启Debug模式'TESTING':                              False,                          # 是否开启测试模式'PROPAGATE_EXCEPTIONS':                 None,                          'PRESERVE_CONTEXT_ON_EXCEPTION':        None,'SECRET_KEY':                           None,'PERMANENT_SESSION_LIFETIME':           timedelta(days=31),'USE_X_SENDFILE':                       False,'LOGGER_NAME':                          None,'LOGGER_HANDLER_POLICY':               'always','SERVER_NAME':                          None,'APPLICATION_ROOT':                     None,'SESSION_COOKIE_NAME':                  'session','SESSION_COOKIE_DOMAIN':                None,'SESSION_COOKIE_PATH':                  None,'SESSION_COOKIE_HTTPONLY':              True,'SESSION_COOKIE_SECURE':                False,'SESSION_REFRESH_EACH_REQUEST':         True,'MAX_CONTENT_LENGTH':                   None,'SEND_FILE_MAX_AGE_DEFAULT':            timedelta(hours=12),'TRAP_BAD_REQUEST_ERRORS':              False,'TRAP_HTTP_EXCEPTIONS':                 False,'EXPLAIN_TEMPLATE_LOADING':             False,'PREFERRED_URL_SCHEME':                 'http','JSON_AS_ASCII':                        True,'JSON_SORT_KEYS':                       True,'JSONIFY_PRETTYPRINT_REGULAR':          True,'JSONIFY_MIMETYPE':                     'application/json','TEMPLATES_AUTO_RELOAD':                None,}方式一：app.config['DEBUG'] = TruePS： 由于Config对象本质上是字典，所以还可以使用app.config.update(...)方式二：1、app.config.from_pyfile("python文件名称")如：settings.pyDEBUG = Trueapp.config.from_pyfile("settings.py")2、app.config.from_envvar("环境变量名称")环境变量的值为python文件名称名称，内部调用from_pyfile方法3、app.config.from_json("json文件名称")JSON文件名称，必须是json格式，因为内部会执行json.loads4、app.config.from_mapping({'DEBUG':True})字典格式5、app.config.from_object("python类或类的路径")  # 从sys.path中已经存在路径开始写举例：app.config.from_object('pro_flask.settings.TestingConfig')settings.pyclass Config(object):DEBUG = FalseTESTING = FalseDATABASE_URI = 'sqlite://:memory:'class ProductionConfig(Config):DATABASE_URI = 'mysql://user@localhost/foo'class DevelopmentConfig(Config):DEBUG = Trueclass TestingConfig(Config):TESTING = TruePS: settings.py文件默认路径要放在程序root_path目录，如果instance_relative_config为True，则就是instance_path目录

三、路由系统

• @app.route('/user/<username>')     # 只有名字
• @app.route('/post/<int:post_id>')    # int 类型
• @app.route('/post/<float:post_id>') # float类型
• @app.route('/post/<path:path>')
• @app.route('/login', methods=['GET', 'POST'])

常用路由系统有以上五种，所有的路由系统都是基于以下对应关系来处理：

DEFAULT_CONVERTERS = {
    'default':          UnicodeConverter,
    'string':           UnicodeConverter,
    'any':              AnyConverter,
    'path':             PathConverter,
    'int':              IntegerConverter,
    'float':            FloatConverter,
    'uuid':             UUIDConverter,
}

注册路由方式

#################### 第一种 ####################
def auth(func):                        def inner(*args, **kwargs):print('before')result = func(*args, **kwargs)print('after')return resultreturn inner@app.route('/index.html',methods=['GET','POST'],endpoint='index') # endpoint 不写默认为函数名 
@auth
def index():return 'Index'#################### 第二种 ####################    
def index():return "Index"
self.add_url_rule(rule='/index.html', endpoint="index", view_func=index, methods=["GET","POST"])
# or
app.add_url_rule(rule='/index.html', endpoint="index", view_func=index, methods=["GET","POST"])
app.view_functions['index'] = index#################### 第三种，CBV ####################
def auth(func):def inner(*args, **kwargs):print('before')result = func(*args, **kwargs)print('after')return resultreturn innerclass IndexView(views.View):methods = ['GET']       # 允许的methoddecorators = [auth, ]   # 装饰器def dispatch_request(self):print('Index')return 'Index!'
app.add_url_rule('/index', view_func=IndexView.as_view(name='index'))  # name=endpoint#################### 第四种 ####################
class IndexView(views.MethodView):methods = ['GET']decorators = [auth, ]def get(self):return 'Index.GET'def post(self):return 'Index.POST'app.add_url_rule('/index', view_func=IndexView.as_view(name='index'))  # name=endpoint#################### 参数 ####################
@app.route和app.add_url_rule参数：rule,                       # URL规则view_func,                  # 视图函数名称defaults=None,              # 默认值,当URL中无参数，函数需要参数时，使用defaults={'k':'v'}为函数提供参数endpoint=None,              # 名称，用于反向生成URL，即： url_for('名称')methods=None,               # 允许的请求方式，如：["GET","POST"]       strict_slashes=None,        # 对URL最后的 / 符号是否严格要求，如：@app.route('/index',strict_slashes=False)  # 访问 www.xx.com/index/ 或 www.xx.com/index均可@app.route('/index',strict_slashes=True)   # 仅访问 http://www.xx.com/index redirect_to=None,           # 重定向到指定地址，如：@app.route('/index/<int:nid>', redirect_to='/home/<nid>')  # 可以是地址def func(adapter, nid):return "/home/888"@app.route('/index/<int:nid>', redirect_to=func)   # 也可以是函数subdomain=None,             # 子域名访问from flask import Flask, views, url_forapp = Flask(import_name=__name__)app.config['SERVER_NAME'] = 'flepeng.com:5000'@app.route("/", subdomain="admin")  # 访问的是admin.flepeng.com:5000def static_index():"""Flask supports static subdomainsThis is available at static.your-domain.tld"""return "static.your-domain.tld"@app.route("/dynamic", subdomain="<username>") # 访问的是xxx.flepeng.com:5000def username_index(username):"""Dynamic subdomains are also supportedTry going to user1.your-domain.tld/dynamic"""return username + ".your-domain.tld"if __name__ == '__main__':app.run()

自定制路由匹配规则

from flask import Flask, views, url_for
from werkzeug.routing import BaseConverterapp = Flask(import_name=__name__)class RegexConverter(BaseConverter):"""自定义URL匹配正则表达式"""def __init__(self, map, regex):super(RegexConverter, self).__init__(map)self.regex = regexdef to_python(self, value):"""路由匹配时，匹配成功后传递给视图函数中参数的值"""return int(value)def to_url(self, value):"""使用url_for反向生成URL时，传递的参数经过该方法处理，返回的值用于生成URL中的参数"""val = super(RegexConverter, self).to_url(value)return val# 添加到flask中
app.url_map.converters['regex'] = RegexConverter@app.route('/index/<regex("\d+"):nid>')
def index(nid):print(url_for('index', nid='888'))return 'Index'if __name__ == '__main__':app.run()

四、模板

1、模板的使用

Flask使用的是Jinja2模板，所以其语法和Django无差别，但是Flask的模板支持的语法更贴近python，支持函数等

2、自定义模板方法

Flask中自定义模板方法的方式和Bottle相似，创建一个函数并通过参数的形式传入render_template，如：

############### html文件 #####################
<!DOCTYPE html>
<html>
<head lang="en"><meta charset="UTF-8"><title></title>
</head>
<body><h1>自定义函数</h1>{{ww()|safe}}
</body>
</html>############### run.py #####################
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flask,render_template
app = Flask(__name__)def index():return '<h1>index</h1>'@app.route('/login', methods=['GET', 'POST'])
def login():return render_template('login.html', ww=index)app.run()############### 其他 html文件 #####################
<!DOCTYPE html>
<html lang="en">
<head><meta charset="UTF-8"><title>Title</title>
</head>
<body>{% macro input(name, type='text', value='') %}<input type="{{ type }}" name="{{ name }}" value="{{ value }}">{% endmacro %}{{ input('n1') }}{% include 'tp.html' %}<h1>asdf{{ v.k1}}</h1>
</body>
</html>

注意：Markup等价django的mark_safe

五、请求和响应

from flask import Flask
from flask import request
from flask import render_template
from flask import redirect
from flask import make_responseapp = Flask(__name__)@app.route('/login.html', methods=['GET', "POST"])
def login():# 请求相关信息 # request.url          http://127.0.0.1/console/editor# request.base_url     http://127.0.0.1/console/editor# request.url_root     http://127.0.0.1# request.host_url     http://127.0.0.1# request.host         127.0.0.1# request.files# f = request.files.get['file_name']   file_name为form表单的name值# f.save('/var/www/uploads/' + secure_filename(f.filename))  secure_filename：检测中文是否合法,f.save会直接保存# 响应相关信息# return "字符串"# return render_template('html模板路径',**{})# return redirect('/index.html')# 自定义响应头# response = make_response(render_template('index.html'))  # response是flask.wrappers.Response类型# response.delete_cookie('key')                    # 删# response.set_cookie('key', 'value')              # 设置cookie# response.headers['X-Something'] = 'A value'      # 设置响应头# return responsereturn "内容"
if __name__ == '__main__':app.run()

request 属性 

六、Session

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。app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'

• 设置：session['username'] ＝ 'xxx'
• 删除：session.pop('username', None)

from flask import Flask, session, redirect, url_for, escape, requestapp = 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 theresession.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'

默认session会存储在cookie中，如下

session源码解析

######################## sessions.py #############################
class SecureCookieSessionInterface(SessionInterface):def open_session(self, app, request):s = self.get_signing_serializer(app)if s is None:return None# 读取val这个val就是session的值,session_cookie_name这个就是配置文件的session_cookie_nameval = request.cookies.get(app.session_cookie_name)if not val:                     # 如果是空的return self.session_class() # 则返回空字典max_age = total_seconds(app.permanent_session_lifetime)try:# 在内部加载，解密，反序列化data = s.loads(val, max_age=max_age)# 又实例化对象return self.session_class(data)except BadSignature:return self.session_class()def save_session(self, app, session, response):domain = self.get_cookie_domain(app)path = self.get_cookie_path(app)# If the session is modified to be empty, remove the cookie.# If the session is empty, return without setting the cookie.if not session:if session.modified:response.delete_cookie(app.session_cookie_name,domain=domain,path=path)return# Add a "Vary: Cookie" header if the session was accessed at all.if session.accessed:response.vary.add('Cookie')if not self.should_set_cookie(app, session):returnhttponly = self.get_cookie_httponly(app)secure = self.get_cookie_secure(app)samesite = self.get_cookie_samesite(app)expires = self.get_expiration_time(app, session)# 对session进行加密，然后dumps编程字符串val = self.get_signing_serializer(app).dumps(dict(session))# 然后在写入用户的浏览器上response.set_cookie(app.session_cookie_name,val,expires=expires,httponly=httponly,domain=domain,path=path,secure=secure,samesite=samesite)

也可以通过重写open-session和save-session方法，让session存储在 内存 中或者 redis 中，

pip3 install Flask-Session
############################# run.py #########################################
from flask import Flask
from flask import session
from pro_flask.utils.session import MySessionInterface
app = Flask(__name__)app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'
app.session_interface = MySessionInterface()
@app.route('/login.html', methods=['GET', "POST"])
def login():print(session)session['user1'] = 'alex'session['user2'] = 'alex'del session['user2']return "内容"if __name__ == '__main__':app.run()############################ session.py ######################
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import uuid
import json
from flask.sessions import SessionInterface
from flask.sessions import SessionMixin
from itsdangerous import Signer, BadSignature, want_bytesclass MySession(dict, SessionMixin):def __init__(self, initial=None, sid=None):self.sid = sidself.initial = initialsuper(MySession, self).__init__(initial or ())def __setitem__(self, key, value):super(MySession, self).__setitem__(key, value)def __getitem__(self, item):return super(MySession, self).__getitem__(item)def __delitem__(self, key):super(MySession, self).__delitem__(key)class MySessionInterface(SessionInterface):session_class = MySessioncontainer = {}def __init__(self):import redisself.redis = redis.Redis()def _generate_sid(self):return str(uuid.uuid4())def _get_signer(self, app):if not app.secret_key:return Nonereturn Signer(app.secret_key, salt='flask-session',key_derivation='hmac')def open_session(self, app, request):"""程序刚启动时执行，需要返回一个session对象"""sid = request.cookies.get(app.session_cookie_name)   # 在cookie中通过配置的name获取sessionif not sid:sid = self._generate_sid()return self.session_class(sid=sid)signer = self._get_signer(app)try:sid_as_bytes = signer.unsign(sid)                # 解密，反序列化sid = sid_as_bytes.decode()except BadSignature:sid = self._generate_sid()return self.session_class(sid=sid)# val = self.redis.get(sid)    # session保存在redis中val = self.container.get(sid)  # session保存在内存中if val is not None:try:data = json.loads(val)return self.session_class(data, sid=sid)except:return self.session_class(sid=sid)return self.session_class(sid=sid)def save_session(self, app, session, response):"""程序结束前执行，可以保存session中所有的值；如： 保存到resit，写入到用户cookie"""domain = self.get_cookie_domain(app)path = self.get_cookie_path(app)httponly = self.get_cookie_httponly(app)secure = self.get_cookie_secure(app)expires = self.get_expiration_time(app, session)val = json.dumps(dict(session))# self.redis.setex(name=session.sid, value=val, time=app.permanent_session_lifetime)  # session保存在redis中self.container.setdefault(session.sid, val)              # session保存在内存中session_id = self._get_signer(app).sign(want_bytes(session.sid))response.set_cookie(app.session_cookie_name, session_id,expires=expires, httponly=httponly,domain=domain, path=path, secure=secure)

也可以使用第三方session，让session存储在redis 中

#!/usr/bin/env python
# -*- coding:utf-8 -*-
"""
pip3 install redis
pip3 install flask-session
"""from flask import Flask, session, redirect
from flask.ext.session import Sessionapp = Flask(__name__)
app.debug = True
app.secret_key = 'asdfasdfasd'app.config['SESSION_TYPE'] = 'redis'
from redis import Redis
app.config['SESSION_REDIS'] = Redis(host='192.168.0.94',port='6379')
Session(app)@app.route('/login')
def login():session['username'] = 'alex'return redirect('/index')@app.route('/index')
def index():name = session['username']return nameif __name__ == '__main__':app.run()

七、蓝图

蓝图用于为应用提供目录划分：

小型应用程序：示例

大型应用程序：示例

其他：

• 蓝图URL前缀：xxx = Blueprint('account', __name__,url_prefix='/xxx')
• 蓝图子域名：xxx = Blueprint('account', __name__,subdomain='admin')
  # 前提需要给配置SERVER_NAME： app.config['SERVER_NAME'] = 'flepeng.com:5000'
  # 访问时：admin.flepeng.com:5000/login.html

######################### count.py #################
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Blueprint
from flask import render_template
from flask import requestaccount = Blueprint('account', __name__)@account.route('/login.html', methods=['GET', "POST"])
def login():
return render_template('login.html')
######################### run.py #################
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flaskapp = Flask(__name__,template_folder='templates',static_folder='statics',static_url_path='/static')from .views.account import account
from .views.blog import blog
from .views.user import userapp.register_blueprint(account)   # 注册
app.register_blueprint(blog)
app.register_blueprint(user)if __name__ == '__main__':app.run

八、message（了解）

message是一个基于Session实现的用于保存数据的集合，其特点是：使用一次就删除。又称闪现

from flask import Flask, flash, redirect, render_template, request, get_flashed_messagesapp = Flask(__name__)
app.secret_key = 'some_secret'@app.route('/')
def index1():messages = get_flashed_messages()print(messages)return "Index1"@app.route('/set')
def index2():v = request.args.get('p')flash(v)return 'ok'if __name__ == "__main__":app.run()

九、中间件（了解）

from flask import Flask, flash, redirect, render_template, requestapp = 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_appdef __call__(self, *args, **kwargs):return self.wsgi_app(*args, **kwargs)if __name__ == "__main__":app.wsgi_app = MiddleWare(app.wsgi_app)app.run(port=9999)

十、请求扩展

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flask, Request, render_templateapp = Flask(__name__, template_folder='templates')
app.debug = True@app.before_first_request     # 只有第一次请求时，会调用，按注册顺序依次执行
def before_first_request1():print('before_first_request1')@app.before_first_request     # 只有第一次请求时，会调用
def before_first_request2():print('before_first_request2')@app.before_request           # 请求之前的处理，按照注册的顺序依次执行，若果有return，则直接返回，返回时经过所有after_request
def before_request1():Request.nnn = 123print('before_request1')@app.before_request
def before_request2():print('before_request2')@app.after_request            # 请求完成之后的处理，按照注册的逆序依次执行
def after_request1(response):print('before_request1', response)return response@app.after_request
def after_request2(response):print('before_request2', response)return response@app.errorhandler(404)         # 当发生错误时执行，比如404错误
def page_not_found(error):return 'This page does not exist', 404@app.context_processor         # 为所有的模板传递的函数，调用方式：{{ val_1 }} 仿佛是jinja2内置的变量一样
def template_var()return {'val_1':'10'}@app.template_global()         # 为所有的模板传递的函数，调用方式：{{ my_fun(1,2) }} 
def my_fun(a1, a2):return a1 + a2@app.template_filter()         # 为所有的模板传递的函数，调用方式{{ 1|db(2,3)}}
def db(a1, a2, a3):return a1 + a2 + a3@app.route('/')
def hello_world():return render_template('hello.html')if __name__ == '__main__':app.run()

十一、Flask插件

• WTForms
• SQLAchemy
• Flask-session
• 等...    

http://flask.pocoo.org/extensions/