Flask是一個基于Python開發并且依賴 jinja2 模板和 Werkzeug WSGI 服務的一個微型框架，對于Werkzeug本質是Socket服務端，其用于接收http請求并對請求進行預處理，然后觸發Flask框架，開發人員基于Flask框架提供的功能對請求進行相應的處理，并返回給用戶，如果要返回給用戶復雜的內容時，需要借助jinja2模板來實現對模板的處理，即：將模板和數據進行渲染，將渲染后的字符串返回給用戶瀏覽器。

“微”(micro) 并不表示你需要把整個 Web 應用塞進單個 Python 文件（雖然確實可以 ），也不意味著 Flask 在功能上有所欠缺。微框架中的“微”意味著 Flask 旨在保持核心簡單而易于擴展。Flask 不會替你做出太多決策——比如使用何種數據庫。而那些 Flask 所選擇的——比如使用何種模板引擎——則很容易替換。除此之外的一切都由可由你掌握。如此，Flask 可以與您珠聯璧合。

默認情況下，Flask 不包含數據庫抽象層、表單驗證，或是其它任何已有多種庫可以勝任的功能。然而，Flask 支持用擴展來給應用添加這些功能，如同是 Flask 本身實現的一樣。眾多的擴展提供了數據庫集成、表單驗證、上傳處理、各種各樣的開放認證技術等功能。Flask 也許是“微小”的，但它已準備好在需求繁雜的生產環境中投入使用。

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中的配置文件是一個flask.config.Config對象（繼承字典）,默認配置為：{'DEBUG':??????????????????????????????? get_debug_flag(default=False),? # 是否開啟Debug模式'TESTING':??????????????????????????????False,????????????????????????? # 是否開啟測試模式'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對象本質上是字典，所以還可以使用app.config.update(...)方式二：1、app.config.from_pyfile("python文件名稱")如：settings.pyDEBUG?=?Trueapp.config.from_pyfile("settings.py")2、app.config.from_envvar("環境變量名稱")環境變量的值為python文件名稱名稱，內部調用from_pyfile方法3、app.config.from_json("json文件名稱")JSON文件名稱，必須是json格式，因為內部會執行json.loads4、app.config.from_mapping({'DEBUG':True})字典格式5、app.config.from_object("python類或類的路徑")  # 從sys.path中已經存在路徑開始寫舉例：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文件默認路徑要放在程序root_path目錄，如果instance_relative_config為True，則就是instance_path目錄

三、路由系統

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

常用路由系統有以上五種，所有的路由系統都是基于以下對應關系來處理：

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

注冊路由方式

#################### 第一種 ####################
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 不寫默認為函數名 
@auth
def index():return 'Index'#################### 第二種 ####################    
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#################### 第三種，CBV ####################
def auth(func):def inner(*args, **kwargs):print('before')result = func(*args, **kwargs)print('after')return resultreturn innerclass IndexView(views.View):methods = ['GET']       # 允許的methoddecorators = [auth, ]   # 裝飾器def dispatch_request(self):print('Index')return 'Index!'
app.add_url_rule('/index', view_func=IndexView.as_view(name='index'))  # name=endpoint#################### 第四種 ####################
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#################### 參數 ####################
@app.route和app.add_url_rule參數：rule,                       # URL規則view_func,                  # 視圖函數名稱defaults=None,              # 默認值,當URL中無參數，函數需要參數時，使用defaults={'k':'v'}為函數提供參數endpoint=None,              # 名稱，用于反向生成URL，即： url_for('名稱')methods=None,               # 允許的請求方式，如：["GET","POST"]       strict_slashes=None,        # 對URL最后的 / 符號是否嚴格要求，如：@app.route('/index',strict_slashes=False)  # 訪問 www.xx.com/index/ 或 www.xx.com/index均可@app.route('/index',strict_slashes=True)   # 僅訪問 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)   # 也可以是函數subdomain=None,             # 子域名訪問from flask import Flask, views, url_forapp = Flask(import_name=__name__)app.config['SERVER_NAME'] = 'flepeng.com:5000'@app.route("/", subdomain="admin")  # 訪問的是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>") # 訪問的是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()

自定制路由匹配規則

from flask import Flask, views, url_for
from werkzeug.routing import BaseConverterapp = Flask(import_name=__name__)class RegexConverter(BaseConverter):"""自定義URL匹配正則表達式"""def __init__(self, map, regex):super(RegexConverter, self).__init__(map)self.regex = regexdef to_python(self, value):"""路由匹配時，匹配成功后傳遞給視圖函數中參數的值"""return int(value)def to_url(self, value):"""使用url_for反向生成URL時，傳遞的參數經過該方法處理，返回的值用于生成URL中的參數"""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，所以其語法和Django無差別，但是Flask的模板支持的語法更貼近python，支持函數等

2、自定義模板方法

Flask中自定義模板方法的方式和Bottle相似，創建一個函數并通過參數的形式傳入render_template，如：

############### html文件 #####################
<!DOCTYPE html>
<html>
<head lang="en"><meta charset="UTF-8"><title></title>
</head>
<body><h1>自定義函數</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等價django的mark_safe

五、請求和響應

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():# 請求相關信息 # 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為form表單的name值# f.save('/var/www/uploads/' + secure_filename(f.filename))  secure_filename：檢測中文是否合法,f.save會直接保存# 響應相關信息# return "字符串"# return render_template('html模板路徑',**{})# return redirect('/index.html')# 自定義響應頭# response = make_response(render_template('index.html'))  # response是flask.wrappers.Response類型# response.delete_cookie('key')                    # 刪# response.set_cookie('key', 'value')              # 設置cookie# response.headers['X-Something'] = 'A value'      # 設置響應頭# return responsereturn "內容"
if __name__ == '__main__':app.run()

request 屬性?

六、Session

除請求對象之外，還有一個 session 對象。它允許你在不同請求間存儲特定用戶的信息。它是在 Cookies 的基礎上實現的，并且對 Cookies 進行密鑰簽名要使用會話，你需要設置一個密鑰。app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'

• 設置：session['username'] ＝ 'xxx'
• 刪除：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'

默認session會存儲在cookie中，如下

session源碼解析

######################## sessions.py #############################
class SecureCookieSessionInterface(SessionInterface):def open_session(self, app, request):s = self.get_signing_serializer(app)if s is None:return None# 讀取val這個val就是session的值,session_cookie_name這個就是配置文件的session_cookie_nameval = request.cookies.get(app.session_cookie_name)if not val:                     # 如果是空的return self.session_class() # 則返回空字典max_age = total_seconds(app.permanent_session_lifetime)try:# 在內部加載，解密，反序列化data = s.loads(val, max_age=max_age)# 又實例化對象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)# 對session進行加密，然后dumps編程字符串val = self.get_signing_serializer(app).dumps(dict(session))# 然后在寫入用戶的瀏覽器上response.set_cookie(app.session_cookie_name,val,expires=expires,httponly=httponly,domain=domain,path=path,secure=secure,samesite=samesite)

也可以通過重寫open-session和save-session方法，讓session存儲在 內存 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 "內容"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):"""程序剛啟動時執行，需要返回一個session對象"""sid = request.cookies.get(app.session_cookie_name)   # 在cookie中通過配置的name獲取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保存在內存中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):"""程序結束前執行，可以保存session中所有的值；如： 保存到resit，寫入到用戶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保存在內存中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，讓session存儲在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、藍圖

藍圖用于為應用提供目錄劃分：

小型應用程序：示例

大型應用程序：示例

其他：

• 藍圖URL前綴：xxx = Blueprint('account', __name__,url_prefix='/xxx')
• 藍圖子域名：xxx = Blueprint('account', __name__,subdomain='admin')
  # 前提需要給配置SERVER_NAME： app.config['SERVER_NAME'] = 'flepeng.com:5000'
  # 訪問時：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)   # 注冊
app.register_blueprint(blog)
app.register_blueprint(user)if __name__ == '__main__':app.run

八、message（了解）

message是一個基于Session實現的用于保存數據的集合，其特點是：使用一次就刪除。又稱閃現

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、中間件（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、請求擴展

#!/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     # 只有第一次請求時，會調用，按注冊順序依次執行
def before_first_request1():print('before_first_request1')@app.before_first_request     # 只有第一次請求時，會調用
def before_first_request2():print('before_first_request2')@app.before_request           # 請求之前的處理，按照注冊的順序依次執行，若果有return，則直接返回，返回時經過所有after_request
def before_request1():Request.nnn = 123print('before_request1')@app.before_request
def before_request2():print('before_request2')@app.after_request            # 請求完成之后的處理，按照注冊的逆序依次執行
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)         # 當發生錯誤時執行，比如404錯誤
def page_not_found(error):return 'This page does not exist', 404@app.context_processor         # 為所有的模板傳遞的函數，調用方式：{{ val_1 }}?仿佛是jinja2內置的變量一樣
def template_var()return {'val_1':'10'}@app.template_global()         # 為所有的模板傳遞的函數，調用方式：{{ my_fun(1,2) }}?
def my_fun(a1, a2):return a1 + a2@app.template_filter()         # 為所有的模板傳遞的函數，調用方式{{ 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/