码迷,mamicode.com
首页 > 其他好文 > 详细

Flask主要知识点

时间:2018-01-30 21:17:40      阅读:1200      评论:0      收藏:0      [点我收藏+]

标签:port   __call__   列表   规则   ima   mysqldb   direct   正则   flask   

  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。

1
pip3 install flask
技术分享图片
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

1
2
3
4
5
6
7
8
9
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

技术分享图片
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] = True
 
    PS: 由于Config对象本质上是字典,所以还可以使用app.config.update(...)
 
方式二:
    app.config.from_pyfile("python文件名称")
        如:
            settings.py
                DEBUG = True
 
            app.config.from_pyfile("settings.py")
 
    import os
    os.environ[‘FLAKS-SETTINGS‘] = ‘settings.py‘
    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
 
 
    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.loads
 
    app.config.from_mapping({DEBUG:True})
        字典格式
 
    app.config.from_object("python类或类的路径")
 
        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: 从sys.path中已经存在路径开始写
     
 
    PS: 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
View Code

 

三、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‘])

  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:

1
2
3
4
5
6
7
8
9
DEFAULT_CONVERTERS = {
    ‘default‘:          UnicodeConverter,
    ‘string‘:           UnicodeConverter,
    ‘any‘:              AnyConverter,
    ‘path‘:             PathConverter,
    ‘int‘:              IntegerConverter,
    ‘float‘:            FloatConverter,
    ‘uuid‘:             UUIDConverter,
}
技术分享图片
        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 Indexdef 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 http://www.xx.com/index/ 或 http://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>)
                                            或
                                            def func(adapter, nid):
                                                return "/home/888"
                                            @app.route(/index/<int:nid>, redirect_to=func)
            subdomain=None,             子域名访问
                                                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.注册路由原理
技术分享图片
           from flask import Flask, views, url_for
            from werkzeug.routing import BaseConverter

            app = 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 = regex

                def 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
                    :param value: 
                    :return: 
                    """
                    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
                    :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. 自定制正则路由匹配

四、视图函数

  在Flask中视图函数也分为CBV和FBV

FBV

技术分享图片
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

技术分享图片
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,所以其语法和Django无差别

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:

技术分享图片
<!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>
html
技术分享图片
#!/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
技术分享图片
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

#全局视图函数,无需在render_template时传入也可在前端调用
#前端使用方式{{sb(1,2)}}
@app.template_global()
def sb(a1, a2):
    return a1 + a2 + 100


#与上面的全局视图函数相似,无需在render_template时传入也可在前端调用
#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()
视图函数扩展
技术分享图片
{% 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等价django的mark_safe

六、请求和响应

技术分享图片
   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():

        # 请求相关信息
        # 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))

        # 响应相关信息
        # return "字符串"
        # return render_template(‘html模板路径‘,**{})
        # return redirect(‘/index.html‘)

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


        return "内容"

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

七、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。

  • 设置:session[‘username‘] = ‘xxx‘

  • 删除:session.pop(‘username‘, None)
技术分享图片
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
技术分享图片
#!/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
技术分享图片
#session.py中用两个类自定义:
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):
        """
        程序刚启动时执行,需要返回一个session对象
        """
        sid = request.cookies.get(app.session_cookie_name)
        if not sid:
            # 生成随机字符串,并将随机字符串添加到 session对象中
            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保存在内存中
        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))

        # session保存在redis中
        # self.redis.setex(name=session.sid, value=val, time=app.permanent_session_lifetime)
        # session保存在内存中
        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(网站的所有session,MySessionInterface.container)
    print(session)
    session[k1] = v1
    session[k2] = v2
    del session[k1]

    # 在内存中操作字典....
    # session[‘k1‘] = ‘v1‘
    # session[‘k2‘] = ‘v2‘
    # del session[‘k1‘]

    return "xx"

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

补充:

  Flask的session与Django有所不同,Flask默认服务器不保存session,当用户来访问时若需要用到session则在内存中生成字典,字典中存放着相应的键值对,然后经过加盐加密后返回给浏览器,浏览器以cookie的形式保存,访问结束后服务器立即删除内存中的session。下次访问时浏览器携带cookie,其中键值对的值就是加密形态的session,经过服务器解密后得到session内容。

  而Django的session则是写入数据库中的,浏览器的cookie只存有sessionid:随机字符串,待下次访问时由随机字符串匹配数据库中的session的键,得到session的值(字典)

 

八、flash(闪现)

  flash是session的一种特殊形式,是一个基于Session实现的用于保存数据的集合,其与普通session的不同之处:使用一次就删除。

技术分享图片
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():
    # 在数据库中添加一条数据
    # 假设添加成功,在跳转到列表页面时,显示添加成功
    # 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

 

九、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(‘xxx‘, __name__,url_prefix=‘/xxx‘)
  • 蓝图子域名:xxx = Blueprint(‘xxx‘, __name__,subdomain=‘admin‘)
    # 使用子域名前提需要给配置SERVER_NAME: app.config[‘SERVER_NAME‘] = ‘helloworld.com:5000‘
    # 访问时:admin.helloworld.com:5000/login.html

 实例说明:

技术分享图片

技术分享图片
import fcrm

if __name__ == __main__:
    fcrm.app.run(port=8001)
manage.py
技术分享图片
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
技术分享图片
from flask import Blueprint,render_template

account = Blueprint(account,__name__)

@account.route(/login)
def login():
    # return ‘Login‘
    return render_template(login.html)
account.py
技术分享图片
from flask import Blueprint

order = Blueprint(order,__name__)

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

 

十、请求扩展(Flask中的类似于Django中间件的功能)

技术分享图片
#!/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
技术分享图片
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

十一、数据库连接池(DButils)

   在Flask中创建多线程,在程序运行时若想对数据库进行操作需建立连接。若每次都进行连接的创建,就会使连接数太多,费时费资源;若直接加锁则不能支持并发。所以这里我们引入数据库连接池来解决问题。

安装

pip3 install dbutils

使用方法:

技术分享图片
from flask import Flask
import time
import pymysql
import threading
from DBUtils.PooledDB import PooledDB, SharedDBConnection
POOL = PooledDB(
    creator=pymysql,  # 使用链接数据库的模块
    maxconnections=6,  # 连接池允许的最大连接数,0和None表示不限制连接数
    mincached=2,  # 初始化时,链接池中至少创建的空闲的链接,0表示不创建
    maxcached=5,  # 链接池中最多闲置的链接,0和None不限制
    maxshared=3,  # 链接池中最多共享的链接数量,0和None表示全部共享。PS: 无用,因为pymysql和MySQLdb等模块的 threadsafety都为1,所有值无论设置为多少,_maxcached永远为0,所以永远是所有链接都共享。
    blocking=True,  # 连接池中如果没有可用连接后,是否阻塞等待。True,等待;False,不等待然后报错
    maxusage=None,  # 一个链接最多被重复使用的次数,None表示无限制
    setsession=[],  # 开始会话前执行的命令列表。如:["set datestyle to ...", "set time zone ..."]
    ping=0,
    # ping MySQL服务端,检查是否服务可用。# 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:缺点:每次请求反复创建数据库连接,连接数太多
    # 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:缺点,不能支持并发
    # 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:基于DBUtils实现数据连接池
    #   - 为每个线程创建一个连接,该线程关闭时,不是真正关闭;本线程再次调用时,还是使用的最开始创建的连接。直到线程终止,数据库连接才关闭。
    #   - 创建一个连接池(10个连接),为所有线程提供连接,使用时来进行获取,使用完毕后,再次放回到连接池。
    #         PS:

    #检测当前正在运行连接数的是否小于最大链接数,如果不小于则:等待或报raise TooManyConnections异常
    # 否则
    # 则优先去初始化时创建的链接中获取链接 SteadyDBConnection。
    # 然后将SteadyDBConnection对象封装到PooledDedicatedDBConnection中并返回。
    # 如果最开始创建的链接没有链接,则去创建一个SteadyDBConnection对象,再封装到PooledDedicatedDBConnection中并返回。
    # 一旦关闭链接后,连接就返回到连接池让后续线程继续使用。
    conn = POOL.connection()
    cursor = conn.cursor()
    cursor.execute(select * from tb1)
    result = cursor.fetchall()
    conn.close()


    return 执行成功



if __name__ == __main__:

    app.run()
数据库连接池

扩展:用类的自定义方法解耦数据库连接池的数据库操作

技术分享图片
#用类的自定义方法解耦数据库连接池的数据库操作


#创建数据库连接池
import pymysql
import threading
from DBUtils.PooledDB import PooledDB, SharedDBConnection
POOL = PooledDB(
    creator=pymysql,  # 使用链接数据库的模块
    maxconnections=6,  # 连接池允许的最大连接数,0和None表示不限制连接数
    mincached=2,  # 初始化时,链接池中至少创建的空闲的链接,0表示不创建
    maxcached=5,  # 链接池中最多闲置的链接,0和None不限制
    maxshared=3,  # 链接池中最多共享的链接数量,0和None表示全部共享。PS: 无用,因为pymysql和MySQLdb等模块的 threadsafety都为1,所有值无论设置为多少,_maxcached永远为0,所以永远是所有链接都共享。
    blocking=True,  # 连接池中如果没有可用连接后,是否阻塞等待。True,等待;False,不等待然后报错
    maxusage=None,  # 一个链接最多被重复使用的次数,None表示无限制
    setsession=[],  # 开始会话前执行的命令列表。如:["set datestyle to ...", "set time zone ..."]
    ping=0,
    # ping MySQL服务端,检查是否服务可用。# 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
)





#定义用于解耦操作的类
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()



#调用(可以是在其他文件下,只要引入上述代码所在文件即可)
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
用类的自定义方法解耦数据库连接池的数据库操作

 

 

十二、Flask的__call__源码解析

  Flask执行app.run()时即执行Flask类的__call__方法

技术分享图片
import sys
from itertools import chain
from .globals import _request_ctx_stack, _app_ctx_stack



#flask\app.py:
class Flask(_PackageBoundObject):
    #1、执行__call__方法
    def __call__(self, environ, start_response):
        return self.wsgi_app(environ, start_response)
    #2、执行Flask类的wsgi_app方法
    def wsgi_app(self, environ, start_response):
        #2.1、执行Flask类的request_context(environ),最后得到封装了request和session的对象
        ctx = self.request_context(environ)#RequestContext类的对象
        #3、在ctx.py中的RequestContext类中执行push堆栈操作
        ctx.push()
        error = None
        try:
            try:
                #4、执行Flask类的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、实例化了ctx.py中的RequestContext类赋值给2中的ctx,执行其构造方法
        return RequestContext(self, environ)#self=app

    #2.3.1、得到Werkzeug 模块提供的Request
    request_class = Request

    #2.4、封装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、执行before_first_request方法,只执行一次
        self.try_trigger_before_first_request_functions()
        try:
            #执行信号
            request_started.send(self)
            #5、执行Flask类的preprocess_request方法,类似Django中间件的装饰器函数
            rv = self.preprocess_request()#rv是装饰器函数的返回值
            if rv is None:#装饰器函数没有返回值,执行视图函数
                # 6、执行Flask类的dispatch_request方法,即视图函数
                rv = self.dispatch_request()
        except Exception as e:
            rv = self.handle_user_exception(e)
           #7、执行Flask类的finalize_request方法,试图函数结束后执行的装饰器
        return self.finalize_request(rv)

    # 5、执行Flask类的preprocess_request方法,类似Django中间件的装饰器函数
    def preprocess_request(self):
        #top读栈中的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、执行Flask类的dispatch_request方法,即视图函数
    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、执行Flask类的finalize_request方法,试图函数结束后执行的装饰器
    def finalize_request(self, rv, from_error_handler=False):

        response = self.make_response(rv)
        try:
            #8、执行Flask类的process_response方法,处理session
            response = self.process_response(response)
            #信号
            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、执行Flask类的process_response方法,处理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、如果没有request的话,执行Flask类下的request_class静态字段
        if request is None:
            request = app.request_class(environ)
        #2.3.2、有request
        self.request = request
        #2.4、执行Flask类下的create_url_adapter方法封装request
        self.url_adapter = app.create_url_adapter(self.request)
        #2.5、默认flashes和session为None
        self.flashes = None
        self.session = None

    #3、堆栈操作
    def push(self):
        # _request_ctx_stack=LocalStack(),由文件导入过来,是一个字典
        top = _request_ctx_stack.top#top是读栈
        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 堆栈操作
        _request_ctx_stack.push(self)
        #查看session,如果没有的话赋予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__: {线程或协程唯一标识: {"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、堆栈操作
    def push(self, obj):
        """Pushes a new item to the stack"""
        rv = getattr(self._local, stack, None)#找牛逼的字典中有没有叫stack的键,默认为None
        if rv is None:#如果是None的话,在牛逼的字典中创建"stack":[]
            self._local.stack = rv = []
        rv.append(obj)#将obj放入[],真正的堆栈操作
        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__:{线程或协程唯一标识:{"stack":[request]},}.赋值给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执行app.run()时源码流程

 

 

十三、信号 blinker

安装  pip3 install blinker

  Flask有10个内置信号,信号是什么呢,是请求执行时会自动执行的一些方法,没有返回值。信号在源码中靠send触发。

内置信号:

技术分享图片
2. request_started = _signals.signal(request-started)                # 请求到来前执行
5. request_finished = _signals.signal(request-finished)              # 请求结束后执行
                 
3. before_render_template = _signals.signal(before-render-template)  # 模板渲染前执行
4. template_rendered = _signals.signal(template-rendered)            # 模板渲染后执行
                 
2/3/4/5或不执行 got_request_exception = _signals.signal(got-request-exception)    # 请求执行出现异常时执行
                 
6. request_tearing_down = _signals.signal(request-tearing-down)      # 请求执行完毕后自动执行(无论成功与否)
7. appcontext_tearing_down = _signals.signal(appcontext-tearing-down)# 请求上下文执行完毕后自动执行(无论成功与否)
                 
                 
1. appcontext_pushed = _signals.signal(appcontext-pushed)            # 请求app上下文push时执行
                
8. appcontext_popped = _signals.signal(appcontext-popped)            # 请求上下文pop时执行
                
最后.message_flashed = _signals.signal(message-flashed)                   # 调用flask在其中添加数据时,自动触发
内置十个信号

  信号用于做什么?

    主要是用于降低代码之间的耦合

  特殊的装饰器和信号有什么区别?  

    装饰器返回值有意义

自定义信号:

  作用:发送短信,邮件,微信     

技术分享图片
from flask import Flask,flash
from flask.signals import _signals
app = Flask(__name__)
mysignal = _signals.signal(mysignal)#实质上是一个列表


# 定义函数
def fun1(*args,**kwargs):
    print(函数一,args,kwargs)

# 定义函数
def fun2(*args,**kwargs):
    print(函数二,args,kwargs)

# 将函数注册到request_started信号中: 添加到这个列表
mysignal.connect(fun1)
mysignal.connect(fun2)




@app.route(/index)
def index():
    # 触发这个信号:执行注册到列表中的所有函数
    # 自定义信号的作用:发送短信,邮件,微信     
    mysignal.send(sender=xxx,a1=123,a2=456)
    return "xx"

if __name__ == __main__:
    app.__call__
    app.run()
自定义信号

 

十四、Flask插件

 

十五、项目须知

 

 

 

 

 

Flask主要知识点

标签:port   __call__   列表   规则   ima   mysqldb   direct   正则   flask   

原文地址:https://www.cnblogs.com/zhuminghui/p/8386955.html

(0)
(0)
   
举报
评论 一句话评论(0
登录后才能评论!
© 2014 mamicode.com 版权所有  联系我们:gaon5@hotmail.com
迷上了代码!