Flask主要知識點


  Flask是一個基於Python開發並且依賴jinja2模板和Werkzeug WSGI服務的一個微型框架,對於Werkzeug本質是Socket服務端,其用於接收http請求並對請求進行預處理,然后觸發Flask框架,開發人員基於Flask框架提供的功能對請求進行相應的處理,並返回給用戶,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) 並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 旨在保持核心簡單而易於擴展。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,但它已准備好在需求繁雜的生產環境中投入使用。

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pip3 install flask
from werkzeug.wrappers import Request, Response

@Request.application
def hello(request):
    return Response('Hello World!')

if __name__ == '__main__':
    from werkzeug.serving import run_simple
    run_simple('localhost', 4000, hello)
werkzeug

一. 基本使用

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from flask import Flask
app = 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'] = True
 
    PS: 由於Config對象本質上是字典,所以還可以使用app.config.update(...)
 
方式二:
    app.config.from_pyfile("python文件名稱")
        如:
            settings.py
                DEBUG = True
 
            app.config.from_pyfile("settings.py")
 
    import os
    os.environ['FLAKS-SETTINGS'] = 'settings.py'
    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
 
 
    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.loads
 
    app.config.from_mapping({'DEBUG':True})
        字典格式
 
    app.config.from_object("python類或類的路徑")
 
        app.config.from_object('pro_flask.settings.TestingConfig')
 
        settings.py
 
            class Config(object):
                DEBUG = False
                TESTING = False
                DATABASE_URI = 'sqlite://:memory:'
 
            class ProductionConfig(Config):
                DATABASE_URI = 'mysql://user@localhost/foo'
 
            class DevelopmentConfig(Config):
                DEBUG = True
 
            class TestingConfig(Config):
                TESTING = True
 
        PS: 從sys.path中已經存在路徑開始寫
     
 
    PS: 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
View Code

 

三、路由系統

  • @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'])

  常用路由系統有以上五種,所有的路由系統都是基於以下對應關系來處理:

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DEFAULT_CONVERTERS = {
     'default' :          UnicodeConverter,
     'string' :           UnicodeConverter,
     'any' :              AnyConverter,
     'path' :             PathConverter,
     'int' :              IntegerConverter,
     'float' :            FloatConverter,
     'uuid' :             UUIDConverter,
}
        def auth(func):
            def inner(*args, **kwargs):
                print('before')
                result = func(*args, **kwargs)
                print('after')
                return result

        return inner

        @app.route('/index.html',methods=['GET','POST'],endpoint='index')
        @auth
        def index():
            return 'Index'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


        或
        def auth(func):
            def inner(*args, **kwargs):
                print('before')
                result = func(*args, **kwargs)
                print('after')
                return result

        return inner

        class IndexView(views.View):
            methods = ['GET']
            decorators = [auth, ]

            def dispatch_request(self):
                print('Index')
                return 'Index!'

        app.add_url_rule('/index', view_func=IndexView.as_view(name='index'))  # name=endpoint
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




        @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,用於反向生成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 http://www.xx.com/index/ 或 http://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>')
                                            或
                                            def func(adapter, nid):
                                                return "/home/888"
                                            @app.route('/index/<int:nid>', redirect_to=func)
            subdomain=None,             子域名訪問
                                                from flask import Flask, views, url_for

                                                app = Flask(import_name=__name__)
                                                app.config['SERVER_NAME'] = 'wupeiqi.com:5000'


                                                @app.route("/", subdomain="admin")
                                                def static_index():
                                                    """Flask supports static subdomains
                                                    This is available at static.your-domain.tld"""
                                                    return "static.your-domain.tld"


                                                @app.route("/dynamic", subdomain="<username>")
                                                def username_index(username):
                                                    """Dynamic subdomains are also supported
                                                    Try going to user1.your-domain.tld/dynamic"""
                                                    return username + ".your-domain.tld"


                                                if __name__ == '__main__':
                                                    app.run()
        
a.注冊路由原理
           from flask import Flask, views, url_for
            from werkzeug.routing import BaseConverter

            app = 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 = regex

                def 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
                    :param value: 
                    :return: 
                    """
                    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,返回的值用於生成URL中的參數
                    :param value: 
                    :return: 
                    """
                    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()
b. 自定制正則路由匹配

四、視圖函數

  在Flask中視圖函數也分為CBV和FBV

FBV

def auth(func):
    def inner(*args, **kwargs):
        result = func(*args, **kwargs)
        return result
    return inner


方式一:
@app.route('/index',endpoint='xx')
@auth
def index(nid):
    url_for('xx',nid=123)
    return "Index"
            


方式二:                
@auth                
def index(nid):
    url_for('xx',nid=123)
    return "Index"

app.add_url_rule('/index',index)
FBV

CBV

def auth(func):
    def inner(*args, **kwargs):
        result = func(*args, **kwargs)
        return result
    return inner

class IndexView(views.MethodView):
    # methods = ['POST']

    decorators = [auth,]
    def get(self):
        v = url_for('index')
        print(v)
        return "GET"

    def post(self):
        return "GET"

app.add_url_rule('/index', view_func=IndexView.as_view(name='index'))
CBV

 

五、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

2、自定義模板方法

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

<!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>
html
#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flask,render_template
app = Flask(__name__)
 
 
def wupeiqi():
    return '<h1>Wupeiqi</h1>'
 
@app.route('/login', methods=['GET', 'POST'])
def login():
    return render_template('login.html', ww=wupeiqi)
 
app.run()
run.py
from flask import Flask,url_for,request,redirect,render_template,jsonify,make_response,Markup
from urllib.parse import urlencode,quote,unquote
app = Flask(__name__)

def test(a1,a2):
    return a1+a2

#全局視圖函數,無需在render_template時傳入也可在前端調用
#前端使用方式{{sb(1,2)}}
@app.template_global()
def sb(a1, a2):
    return a1 + a2 + 100


#與上面的全局視圖函數相似,無需在render_template時傳入也可在前端調用
#前端使用方式{{ 1|db(2,3)}}
@app.template_filter()
def db(a1, a2, a3):
    return a1 + a2 + a3



@app.route('/index',endpoint='xx')
def index():
    v1 = "字符串"
    v2 = [11,22,33]
    v3 = {'k1':'v1','k2':'v2'}
    v4 = Markup("<input type='text' />")#若不使用Markup,前端需{{v4|safe}}
    return render_template('index.html',v1=v1,v2=v2,v3=v3,v4=v4,test=test)


if __name__ == '__main__':
    # app.__call__
    app.run()
視圖函數擴展
{% extends 'layout.html'%}

{%block body %}
    {{v1}}

    <ul>
        {% for item in v2 %}
        <li>{{item}}</li>
        {% endfor %}
    </ul>
    {{v2.1}}

    <ul>
        {% for k,v in v3.items() %}
        <li>{{k}}  {{v}}</li>
        {% endfor %}
    </ul>
    {{v3.k1}}
    {{v3.get('k1')}}

    {{v4}}
    <!--{{v4|safe}}-->

    <h1>{{test(1,19)}}</h1>

    {{sb(1,2)}}

    {{ 1|db(2,3)}}


    {% macro xxxx(name, type='text', value='') %}
        <input type="{{ type }}" name="{{ name }}" value="{{ value }}">
        <input type="{{ type }}" name="{{ name }}" value="{{ value }}">
        <input type="{{ type }}" name="{{ name }}" value="{{ value }}">
        <input type="{{ type }}" name="{{ name }}" value="{{ value }}">
    {% endmacro %}

    {{ xxxx('n1') }}


{%endblock%}
index.html

注意:Markup等價django的mark_safe

六、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_response

    app = Flask(__name__)


    @app.route('/login.html', methods=['GET', "POST"])
    def login():

        # 請求相關信息
        # request.method
        # request.args
        # request.form
        # request.values
        # 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
        # request.files
        # obj = request.files['the_file_name']
        # obj.save('/var/www/uploads/' + secure_filename(f.filename))

        # 響應相關信息
        # return "字符串"
        # return render_template('html模板路徑',**{})
        # return redirect('/index.html')

        # response = make_response(render_template('index.html'))
        # response是flask.wrappers.Response類型
        # response.delete_cookie('key')
        # response.set_cookie('key', 'value')
        # response.headers['X-Something'] = 'A value'
        # return response


        return "內容"

    if __name__ == '__main__':
        app.run()
View Code

七、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,並且對 Cookies 進行密鑰簽名要使用會話,你需要設置一個密鑰。

  • 設置:session['username'] = 'xxx'

  • 刪除:session.pop('username', None)
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'
基本使用
#!/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 Session


app = 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 name


if __name__ == '__main__':
    app.run()
第三方session
#session.py中用兩個類自定義:
import uuid
import json
from flask.sessions import SessionInterface
from flask.sessions import SessionMixin
from itsdangerous import Signer, BadSignature, want_bytes

class MySession(dict, SessionMixin):
    def __init__(self, initial=None, sid=None):
        self.sid = sid
        self.initial = initial
        super(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 = MySession
    container = {
        # 'asdfasdfasdfas':{'k1':'v1','k2':'v2'}
        # 'asdfasdfasdfas':"{'k1':'v1','k2':'v2'}"
    }

    def __init__(self):
        pass
        # import redis
        # self.redis = redis.Redis()

    def _generate_sid(self):
        return str(uuid.uuid4())

    def _get_signer(self, app):
        if not app.secret_key:
            return None
        return 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)
        if not sid:
            # 生成隨機字符串,並將隨機字符串添加到 session對象中
            sid = self._generate_sid()
            return self.session_class(sid=sid)

        signer = self._get_signer(app)
        try:
            sid_as_bytes = signer.unsign(sid)
            sid = sid_as_bytes.decode()
        except BadSignature:
            sid = self._generate_sid()
            return self.session_class(sid=sid)

        # session保存在redis中
        # val = self.redis.get(sid)
        # session保存在內存中
        val = self.container.get(sid)

        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))

        # session保存在redis中
        # self.redis.setex(name=session.sid, value=val, time=app.permanent_session_lifetime)
        # session保存在內存中
        self.container.setdefault(session.sid, val)

        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)





#run.py:
from flask import Flask,request,session
app = Flask(__name__)
app.secret_key = 'sdfsdfsd'
app.session_interface = MySessionInterface()
# app.session_interface
# app.make_null_session()
@app.route('/index')
def index():
    print('網站的所有session',MySessionInterface.container)
    print(session)
    session['k1'] = 'v1'
    session['k2'] = 'v2'
    del session['k1']

    # 在內存中操作字典....
    # session['k1'] = 'v1'
    # session['k2'] = 'v2'
    # del session['k1']

    return "xx"

if __name__ == '__main__':
    app.run()
自定義session

補充:

  Flask的session與Django有所不同,Flask默認服務器不保存session,當用戶來訪問時若需要用到session則在內存中生成字典,字典中存放着相應的鍵值對,然后經過加鹽加密后返回給瀏覽器,瀏覽器以cookie的形式保存,訪問結束后服務器立即刪除內存中的session。下次訪問時瀏覽器攜帶cookie,其中鍵值對的值就是加密形態的session,經過服務器解密后得到session內容。

  而Django的session則是寫入數據庫中的,瀏覽器的cookie只存有sessionid:隨機字符串,待下次訪問時由隨機字符串匹配數據庫中的session的鍵,得到session的值(字典)

 

八、跨域請求

  跨域請求問題一直都是web項目的第一門檻,Flask 處理跨域請求需要導入一個模塊 flask_cors

pip install flask_cors
from flask import Flask
from flask_cors import *

app = Flask(__name__)
CORS(app, supports_credentials=True) # 用於允許跨域請求

 

 

九、flash(閃現)

  flash是session的一種特殊形式,是一個基於Session實現的用於保存數據的集合,其與普通session的不同之處:使用一次就刪除。

from flask import Flask,session,Session,flash,get_flashed_messages,redirect,render_template,request
app = Flask(__name__)
app.secret_key ='sdfsdfsdf'

@app.route('/users')
def users():
    # msg = request.args.get('msg','')
    # msg = session.get('msg')
    # if msg:
    #     del session['msg']

    v = get_flashed_messages()
    print(v)
    msg = ''
    return render_template('users.html',msg=msg)

@app.route('/useradd')
def user_add():
    # 在數據庫中添加一條數據
    # 假設添加成功,在跳轉到列表頁面時,顯示添加成功
    # return redirect('/users?msg=添加成功')
    # session['msg'] = '添加成功'

    flash('添加成功')
    return redirect('/users')


if __name__ == '__main__':
    app.run()
flash用法

 

十、藍圖

藍圖用於為應用提供目錄划分:

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('xxx', __name__,url_prefix='/xxx')
  • 藍圖子域名:xxx = Blueprint('xxx', __name__,subdomain='admin')
    # 使用子域名前提需要給配置SERVER_NAME: app.config['SERVER_NAME'] = 'helloworld.com:5000'
    # 訪問時:admin.helloworld.com:5000/login.html

 實例說明:

import fcrm

if __name__ == '__main__':
    fcrm.app.run(port=8001)
manage.py
from flask import Flask
from .views import account
from .views import order

app = Flask(__name__)
print(app.root_path)
app.register_blueprint(account.account)
app.register_blueprint(order.order)
__init__.py
from flask import Blueprint,render_template

account = Blueprint('account',__name__)

@account.route('/login')
def login():
    # return 'Login'
    return render_template('login.html')
account.py
from flask import Blueprint

order = Blueprint('order',__name__)

@order.route('/order')
def login():
    return 'Order'
order.py

 

十一、請求擴展(Flask中的類似於Django中間件的功能)

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flask, Request, render_template

app = Flask(__name__, template_folder='templates')
app.debug = True


@app.before_first_request
def before_first_request1():
    print('before_first_request1')


@app.before_first_request
def before_first_request2():
    print('before_first_request2')


@app.before_request
def before_request1():
    Request.nnn = 123
    print('before_request1')


@app.before_request
def before_request2():
    print('before_request2')


@app.after_request
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)
def page_not_found(error):
    return 'This page does not exist', 404


@app.template_global()
def sb(a1, a2):
    return a1 + a2


@app.template_filter()
def db(a1, a2, a3):
    return a1 + a2 + a3


@app.route('/')
def hello_world():
    return render_template('hello.html')


if __name__ == '__main__':
    app.run()
方式一
from flask import Flask,session,Session,flash,get_flashed_messages,redirect,render_template,request
app = Flask(__name__)
app.secret_key ='sdfsdfsdf'

@app.before_request
def process_request1():
    print('process_request1')

@app.after_request
def process_response1(response):
    print('process_response1')
    return response


@app.before_request
def process_request2():
    print('process_request2')

@app.after_request
def process_response2(response):
    print('process_response2')
    return response


@app.route('/index')
def index():
    print('index')
    return 'Index'

@app.route('/order')
def order():
    print('order')
    return 'order'

@app.route('/test')
def test():
    print('test')
    return 'test'

if __name__ == '__main__':
    app.run()
方式二

十二、數據庫連接池(DButils)

   在Flask中創建多線程,在程序運行時若想對數據庫進行操作需建立連接。若每次都進行連接的創建,就會使連接數太多,費時費資源;若直接加鎖則不能支持並發。所以這里我們引入數據庫連接池來解決問題。

安裝

pip3 install dbutils

使用方法:

from flask import Flask
import time
import pymysql
import threading
from DBUtils.PooledDB import PooledDB, SharedDBConnection
POOL = PooledDB(
    creator=pymysql,  # 使用鏈接數據庫的模塊
    maxconnections=6,  # 連接池允許的最大連接數,0和None表示不限制連接數
    mincached=2,  # 初始化時,鏈接池中至少創建的空閑的鏈接,0表示不創建
    maxcached=5,  # 鏈接池中最多閑置的鏈接,0和None不限制
    maxshared=3,  # 鏈接池中最多共享的鏈接數量,0和None表示全部共享。PS: 無用,因為pymysql和MySQLdb等模塊的 threadsafety都為1,所有值無論設置為多少,_maxcached永遠為0,所以永遠是所有鏈接都共享。
    blocking=True,  # 連接池中如果沒有可用連接后,是否阻塞等待。True,等待;False,不等待然后報錯
    maxusage=None,  # 一個鏈接最多被重復使用的次數,None表示無限制
    setsession=[],  # 開始會話前執行的命令列表。如:["set datestyle to ...", "set time zone ..."]
    ping=0,
    # ping MySQL服務端,檢查是否服務可用。# 如:0 = None = never, 1 = default = whenever it is requested, 2 = when a cursor is created, 4 = when a query is executed, 7 = always
    host='127.0.0.1',
    port=3306,
    user='root',
    password='123',
    database='pooldb',
    charset='utf8'
)


app = Flask(__name__)
app.secret_key ='sdfsdfsdf'



@app.route('/index')
def index():
    # 第一步:缺點:每次請求反復創建數據庫連接,連接數太多
    # conn = pymysql.connect()
    # cursor = conn.cursor()
    # cursor.execute('select * from tb where id > %s',[5,])
    # result = cursor.fetchall()
    # cursor.close()
    # conn.close()
    # print(result)

    # 第二步:缺點,不能支持並發
    # pymysql.threadsafety
    # with LOCK:
    #     cursor = CONN.cursor()
    #     cursor.execute('select * from tb where id > %s', [5, ])
    #     result = cursor.fetchall()
    #     cursor.close()
    #
    #     print(result)

    # 第三步:基於DBUtils實現數據連接池
    #   - 為每個線程創建一個連接,該線程關閉時,不是真正關閉;本線程再次調用時,還是使用的最開始創建的連接。直到線程終止,數據庫連接才關閉。
    #   - 創建一個連接池(10個連接),為所有線程提供連接,使用時來進行獲取,使用完畢后,再次放回到連接池。
    #         PS:

    #檢測當前正在運行連接數的是否小於最大鏈接數,如果不小於則:等待或報raise TooManyConnections異常
    # 否則
    # 則優先去初始化時創建的鏈接中獲取鏈接 SteadyDBConnection。
    # 然后將SteadyDBConnection對象封裝到PooledDedicatedDBConnection中並返回。
    # 如果最開始創建的鏈接沒有鏈接,則去創建一個SteadyDBConnection對象,再封裝到PooledDedicatedDBConnection中並返回。
    # 一旦關閉鏈接后,連接就返回到連接池讓后續線程繼續使用。
    conn = POOL.connection()
    cursor = conn.cursor()
    cursor.execute('select * from tb1')
    result = cursor.fetchall()
    conn.close()


    return '執行成功'



if __name__ == '__main__':

    app.run()
數據庫連接池

擴展:用類的自定義方法解耦數據庫連接池的數據庫操作

#用類的自定義方法解耦數據庫連接池的數據庫操作


#創建數據庫連接池
import pymysql
import threading
from DBUtils.PooledDB import PooledDB, SharedDBConnection
POOL = PooledDB(
    creator=pymysql,  # 使用鏈接數據庫的模塊
    maxconnections=6,  # 連接池允許的最大連接數,0和None表示不限制連接數
    mincached=2,  # 初始化時,鏈接池中至少創建的空閑的鏈接,0表示不創建
    maxcached=5,  # 鏈接池中最多閑置的鏈接,0和None不限制
    maxshared=3,  # 鏈接池中最多共享的鏈接數量,0和None表示全部共享。PS: 無用,因為pymysql和MySQLdb等模塊的 threadsafety都為1,所有值無論設置為多少,_maxcached永遠為0,所以永遠是所有鏈接都共享。
    blocking=True,  # 連接池中如果沒有可用連接后,是否阻塞等待。True,等待;False,不等待然后報錯
    maxusage=None,  # 一個鏈接最多被重復使用的次數,None表示無限制
    setsession=[],  # 開始會話前執行的命令列表。如:["set datestyle to ...", "set time zone ..."]
    ping=0,
    # ping MySQL服務端,檢查是否服務可用。# 如:0 = None = never, 1 = default = whenever it is requested, 2 = when a cursor is created, 4 = when a query is executed, 7 = always
    host='47.93.4.198',
    port=3306,
    user='root',
    password='123',
    database='s6',
    charset='utf8'
)





#定義用於解耦操作的類
class SQLHelper(object):

    def __init__(self):
        self.conn = None
        self.cursor = None

    def open(self,cursor=pymysql.cursors.DictCursor):
        self.conn = db_pool.POOL.connection()
        self.cursor = self.conn.cursor(cursor=cursor)

    def close(self):
        self.cursor.close()
        self.conn.close()

    def fetchone(self,sql,params):
        cursor = self.cursor
        cursor.execute(sql,params)
        result = cursor.fetchone()

        return result

    def fetchall(self, sql, params):
        cursor = self.cursor
        cursor.execute(sql, params)
        result = cursor.fetchall()
        return result

    def __enter__(self):
        self.open()
        return self

    def __exit__(self, exc_type, exc_val, exc_tb):
        self.close()



#調用(可以是在其他文件下,只要引入上述代碼所在文件即可)
with SQLHelper() as helper:
    result = helper.fetchone('select * from users where name=%s and pwd = %s',[request.form.get('user'),request.form.get('pwd'),])
    if result:
        #做操作
用類的自定義方法解耦數據庫連接池的數據庫操作

 

 

十三、Flask的__call__源碼解析

  Flask執行app.run()時即執行Flask類的__call__方法

import sys
from itertools import chain
from .globals import _request_ctx_stack, _app_ctx_stack



#flask\app.py:
class Flask(_PackageBoundObject):
    #1、執行__call__方法
    def __call__(self, environ, start_response):
        return self.wsgi_app(environ, start_response)
    #2、執行Flask類的wsgi_app方法
    def wsgi_app(self, environ, start_response):
        #2.1、執行Flask類的request_context(environ),最后得到封裝了request和session的對象
        ctx = self.request_context(environ)#RequestContext類的對象
        #3、在ctx.py中的RequestContext類中執行push堆棧操作
        ctx.push()
        error = None
        try:
            try:
                #4、執行Flask類的full_dispatch_request方法
                response = self.full_dispatch_request()
            except Exception as e:
                error = e
                response = self.handle_exception(e)
            except:
                error = sys.exc_info()[1]
                raise
            return response(environ, start_response)
        finally:
            if self.should_ignore_error(error):
                error = None
            ctx.auto_pop(error)

    #2.1
    def request_context(self, environ):
        #2.2、實例化了ctx.py中的RequestContext類賦值給2中的ctx,執行其構造方法
        return RequestContext(self, environ)#self=app

    #2.3.1、得到Werkzeug 模塊提供的Request
    request_class = Request

    #2.4、封裝request
    def create_url_adapter(self, request):
        """Creates a URL adapter for the given request.  The URL adapter
        is created at a point where the request context is not yet set up
        so the request is passed explicitly.

        .. versionadded:: 0.6

        .. versionchanged:: 0.9
           This can now also be called without a request object when the
           URL adapter is created for the application context.
        """
        if request is not None:
            return self.url_map.bind_to_environ(request.environ,
                server_name=self.config['SERVER_NAME'])
        # We need at the very least the server name to be set for this
        # to work.
        if self.config['SERVER_NAME'] is not None:
            return self.url_map.bind(
                self.config['SERVER_NAME'],
                script_name=self.config['APPLICATION_ROOT'] or '/',
                url_scheme=self.config['PREFERRED_URL_SCHEME'])

    #4、
    def full_dispatch_request(self):
       #4.1、執行before_first_request方法,只執行一次
        self.try_trigger_before_first_request_functions()
        try:
            #執行信號
            request_started.send(self)
            #5、執行Flask類的preprocess_request方法,類似Django中間件的裝飾器函數
            rv = self.preprocess_request()#rv是裝飾器函數的返回值
            if rv is None:#裝飾器函數沒有返回值,執行視圖函數
                # 6、執行Flask類的dispatch_request方法,即視圖函數
                rv = self.dispatch_request()
        except Exception as e:
            rv = self.handle_user_exception(e)
           #7、執行Flask類的finalize_request方法,試圖函數結束后執行的裝飾器
        return self.finalize_request(rv)

    # 5、執行Flask類的preprocess_request方法,類似Django中間件的裝飾器函數
    def preprocess_request(self):
        #top讀棧中的request
        bp = _request_ctx_stack.top.request.blueprint

        funcs = self.url_value_preprocessors.get(None, ())
        if bp is not None and bp in self.url_value_preprocessors:
            funcs = chain(funcs, self.url_value_preprocessors[bp])
        for func in funcs:
            func(request.endpoint, request.view_args)

        funcs = self.before_request_funcs.get(None, ())
        if bp is not None and bp in self.before_request_funcs:
            funcs = chain(funcs, self.before_request_funcs[bp])
        for func in funcs:
            rv = func()
            if rv is not None:
                return rv

    #6、執行Flask類的dispatch_request方法,即視圖函數
    def dispatch_request(self):
        req = _request_ctx_stack.top.request
        if req.routing_exception is not None:
            self.raise_routing_exception(req)
        rule = req.url_rule
        # if we provide automatic options for this URL and the
        # request came with the OPTIONS method, reply automatically
        if getattr(rule, 'provide_automatic_options', False) \
                and req.method == 'OPTIONS':
            return self.make_default_options_response()
        # otherwise dispatch to the handler for that endpoint
        return self.view_functions[rule.endpoint](**req.view_args)

    # 7、執行Flask類的finalize_request方法,試圖函數結束后執行的裝飾器
    def finalize_request(self, rv, from_error_handler=False):

        response = self.make_response(rv)
        try:
            #8、執行Flask類的process_response方法,處理session
            response = self.process_response(response)
            #信號
            request_finished.send(self, response=response)
        except Exception:
            if not from_error_handler:
                raise
            self.logger.exception('Request finalizing failed with an '
                                  'error while handling an error')
        return response

    # 8、執行Flask類的process_response方法,處理session
    def process_response(self, response):

        ctx = _request_ctx_stack.top
        bp = ctx.request.blueprint
        funcs = ctx._after_request_functions
        if bp is not None and bp in self.after_request_funcs:
            funcs = chain(funcs, reversed(self.after_request_funcs[bp]))
        if None in self.after_request_funcs:
            funcs = chain(funcs, reversed(self.after_request_funcs[None]))
        for handler in funcs:
            response = handler(response)
        if not self.session_interface.is_null_session(ctx.session):
            self.save_session(ctx.session, response)
        return response







#ctx.py:
class RequestContext(object):
    #2.2、
    def __init__(self, app, environ, request=None):
        #self=ctx,app=app
        self.app = app
        # 2.3.1、如果沒有request的話,執行Flask類下的request_class靜態字段
        if request is None:
            request = app.request_class(environ)
        #2.3.2、有request
        self.request = request
        #2.4、執行Flask類下的create_url_adapter方法封裝request
        self.url_adapter = app.create_url_adapter(self.request)
        #2.5、默認flashes和session為None
        self.flashes = None
        self.session = None

    #3、堆棧操作
    def push(self):
        # _request_ctx_stack=LocalStack(),由文件導入過來,是一個字典
        top = _request_ctx_stack.top#top是讀棧
        if top is not None and top.preserved:
            top.pop(top._preserved_exc)
        #_app_ctx_stack = LocalStack()
        app_ctx = _app_ctx_stack.top
        if app_ctx is None or app_ctx.app != self.app:
            app_ctx = self.app.app_context()
            app_ctx.push()
            self._implicit_app_ctx_stack.append(app_ctx)
        else:
            self._implicit_app_ctx_stack.append(None)

        if hasattr(sys, 'exc_clear'):
            sys.exc_clear()
        #3.1 堆棧操作
        _request_ctx_stack.push(self)
        #查看session,如果沒有的話賦予NullSession
        self.session = self.app.open_session(self.request)
        if self.session is None:
            self.session = self.app.make_null_session()



#global.py:
from functools import partial
from werkzeug.local import LocalStack, LocalProxy
_request_ctx_stack = LocalStack()
_app_ctx_stack = LocalStack()
current_app = LocalProxy(_find_app)
request = LocalProxy(partial(_lookup_req_object, 'request'))
session = LocalProxy(partial(_lookup_req_object, 'session'))
g = LocalProxy(partial(_lookup_app_object, 'g'))






#local.py:
class LocalStack(object):


    def __init__(self):
        #_request_ctx_stack._local=self._local=__storage__: {線程或協程唯一標識: {"stack": [request]}, }
        self._local = Local()#形成牛逼的字典

    def __release_local__(self):
        self._local.__release_local__()

    def _get__ident_func__(self):
        return self._local.__ident_func__

    def _set__ident_func__(self, value):
        object.__setattr__(self._local, '__ident_func__', value)
    __ident_func__ = property(_get__ident_func__, _set__ident_func__)
    del _get__ident_func__, _set__ident_func__

    def __call__(self):
        def _lookup():
            rv = self.top
            if rv is None:
                raise RuntimeError('object unbound')
            return rv
        return LocalProxy(_lookup)
    #3.1、堆棧操作
    def push(self, obj):
        """Pushes a new item to the stack"""
        rv = getattr(self._local, 'stack', None)#找牛逼的字典中有沒有叫stack的鍵,默認為None
        if rv is None:#如果是None的話,在牛逼的字典中創建"stack":[]
            self._local.stack = rv = []
        rv.append(obj)#將obj放入[],真正的堆棧操作
        return rv

    def pop(self):
        """Removes the topmost item from the stack, will return the
        old value or `None` if the stack was already empty.
        """
        stack = getattr(self._local, 'stack', None)
        if stack is None:
            return None
        elif len(stack) == 1:
            release_local(self._local)
            return stack[-1]
        else:
            return stack.pop()

    @property
    def top(self):
        """The topmost item on the stack.  If the stack is empty,
        `None` is returned.
        """
        try:
            return self._local.stack[-1]
        except (AttributeError, IndexError):
            return None


class Local(object):
    __slots__ = ('__storage__', '__ident_func__')

    def __init__(self):
        #最后得到__storage__:{線程或協程唯一標識:{"stack":[request]},}.賦值給LocalStack()._local,即_request_ctx_stack
        object.__setattr__(self, '__storage__', {})
        object.__setattr__(self, '__ident_func__', get_ident)

    def __iter__(self):
        return iter(self.__storage__.items())

    def __call__(self, proxy):
        """Create a proxy for a name."""
        return LocalProxy(self, proxy)

    def __release_local__(self):
        self.__storage__.pop(self.__ident_func__(), None)

    def __getattr__(self, name):
        try:
            return self.__storage__[self.__ident_func__()][name]
        except KeyError:
            raise AttributeError(name)

    def __setattr__(self, name, value):
        ident = self.__ident_func__()
        storage = self.__storage__
        try:
            storage[ident][name] = value
        except KeyError:
            storage[ident] = {name: value}

    def __delattr__(self, name):
        try:
            del self.__storage__[self.__ident_func__()][name]
        except KeyError:
            raise AttributeError(name)
flask執行app.run()時源碼流程

流程分析:

  1. 執行__call__方法時即執行Flask類的wsgi_app方法。
  2. 在該方法中調用request_context方法用於封裝request和session,默認flashed和session為None。
  3. 然后,在ctx.py中的RequestContext類中執行push堆棧操作,堆棧操作中會查看session,如果沒有的話會賦予NullSession。堆棧操作中會形成一個很大的字典,字典的形式為{線程或協程的唯一id: {"stack": [request]},...}。
  4. 堆棧操作完畢后執行full_dispatch_request方法,該方法主要執行裝飾器(中間件或信號)和視圖函數。首先會執行before_first_request方法,只執行一次。然后執行信號request_started.send(self)。
  5. 接下來執行preprocess_request(),其作用類似於Django的中間件。
  6. 若preprocess_request()沒有返回值即表明通過中間件,執行dispatch_request()即視圖函數。
  7. 視圖函數結束后執行finalize_request()方法,為自定義的裝飾器。
  8. 執行Flask類的process_response方法,處理session。
  9. 最后得到__storage__:{線程或協程唯一標識:{"stack":[request]},}.賦值給LocalStack()._local,即_request_ctx_stack

 

十四、信號 blinker

安裝  pip3 install blinker

  Flask有10個內置信號,信號是什么呢,是請求執行時會自動執行的一些方法,沒有返回值。信號在源碼中靠send觸發。

內置信號:

2. request_started = _signals.signal('request-started')                # 請求到來前執行
5. request_finished = _signals.signal('request-finished')              # 請求結束后執行
                 
3. before_render_template = _signals.signal('before-render-template')  # 模板渲染前執行
4. template_rendered = _signals.signal('template-rendered')            # 模板渲染后執行
                 
2/3/4/5或不執行 got_request_exception = _signals.signal('got-request-exception')    # 請求執行出現異常時執行
                 
6. request_tearing_down = _signals.signal('request-tearing-down')      # 請求執行完畢后自動執行(無論成功與否)
7. appcontext_tearing_down = _signals.signal('appcontext-tearing-down')# 請求上下文執行完畢后自動執行(無論成功與否)
                 
                 
1. appcontext_pushed = _signals.signal('appcontext-pushed')            # 請求app上下文push時執行
                
8. appcontext_popped = _signals.signal('appcontext-popped')            # 請求上下文pop時執行
                
最后.message_flashed = _signals.signal('message-flashed')                   # 調用flask在其中添加數據時,自動觸發
內置十個信號

  信號用於做什么?

    主要是用於降低代碼之間的耦合

  特殊的裝飾器和信號有什么區別?  

    裝飾器返回值有意義

自定義信號:

  作用:發送短信,郵件,微信     

from flask import Flask,flash
from flask.signals import _signals
app = Flask(__name__)
mysignal = _signals.signal('mysignal')#實質上是一個列表


# 定義函數
def fun1(*args,**kwargs):
    print('函數一',args,kwargs)

# 定義函數
def fun2(*args,**kwargs):
    print('函數二',args,kwargs)

# 將函數注冊到request_started信號中: 添加到這個列表
mysignal.connect(fun1)
mysignal.connect(fun2)




@app.route('/index')
def index():
    # 觸發這個信號:執行注冊到列表中的所有函數
    # 自定義信號的作用:發送短信,郵件,微信     
    mysignal.send(sender='xxx',a1=123,a2=456)
    return "xx"

if __name__ == '__main__':
    app.__call__
    app.run()
自定義信號

 

十五、Flask插件

 

十六、項目須知

 

 

 

 

 


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