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。
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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)
一. 基本使用
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from flask import Flaskapp = Flask(__name__)@app.route(‘/‘)def hello_world(): return ‘Hello World!‘if __name__ == ‘__main__‘: app.run() |
二、配置文件
flask中的配置文件是一个flask.config.Config对象（继承字典）,默认配置为： { ‘DEBUG‘: get_debug_flag(default=False), 是否开启Debug模式 ‘TESTING‘: False, 是否开启测试模式 ‘PROPAGATE_EXCEPTIONS‘: None, ‘PRESERVE_CONTEXT_ON_EXCEPTION‘: None, ‘SECRET_KEY‘: None, ‘PERMANENT_SESSION_LIFETIME‘: timedelta(days=31), ‘USE_X_SENDFILE‘: False, ‘LOGGER_NAME‘: None, ‘LOGGER_HANDLER_POLICY‘: ‘always‘, ‘SERVER_NAME‘: None, ‘APPLICATION_ROOT‘: None, ‘SESSION_COOKIE_NAME‘: ‘session‘, ‘SESSION_COOKIE_DOMAIN‘: None, ‘SESSION_COOKIE_PATH‘: None, ‘SESSION_COOKIE_HTTPONLY‘: True, ‘SESSION_COOKIE_SECURE‘: False, ‘SESSION_REFRESH_EACH_REQUEST‘: True, ‘MAX_CONTENT_LENGTH‘: None, ‘SEND_FILE_MAX_AGE_DEFAULT‘: timedelta(hours=12), ‘TRAP_BAD_REQUEST_ERRORS‘: False, ‘TRAP_HTTP_EXCEPTIONS‘: False, ‘EXPLAIN_TEMPLATE_LOADING‘: False, ‘PREFERRED_URL_SCHEME‘: ‘http‘, ‘JSON_AS_ASCII‘: True, ‘JSON_SORT_KEYS‘: True, ‘JSONIFY_PRETTYPRINT_REGULAR‘: True, ‘JSONIFY_MIMETYPE‘: ‘application/json‘, ‘TEMPLATES_AUTO_RELOAD‘: None, } 方式一： app.config[‘DEBUG‘] = 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
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：
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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‘ 或 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 或 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()
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()
四、视图函数
在Flask中视图函数也分为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)
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‘))
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：
<!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>
#!/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()
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()
{% 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%}
注意：Markup等价django的mark_safe
六、请求和响应
from flask import Flask from flask import request from flask import render_template from flask import redirect from flask import make_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()
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。
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设置：session[‘username‘] ＝ ‘xxx‘
- 删除：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‘
#!/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()
#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()
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。
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()
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：
import fcrm if __name__ == ‘__main__‘: fcrm.app.run(port=8001)
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)
from flask import Blueprint,render_template account = Blueprint(‘account‘,__name__) @account.route(‘/login‘) def login(): # return ‘Login‘ return render_template(‘login.html‘)
from flask import Blueprint order = Blueprint(‘order‘,__name__) @order.route(‘/order‘) def login(): return ‘Order‘
十、请求扩展（Flask中的类似于Django中间件的功能）
#!/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()
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()
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：
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()
扩展：用类的自定义方法解耦数据库连接池的数据库操作
#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
十二、Flask的__call__源码解析
Flask执行app.run()时即执行Flask类的__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、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)
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：
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
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
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()
十四、Flask插件
- flask-script
- wtforms
- SQLAlchemy
- 等... http://flask.pocoo.org/extensions/
十五、项目须知
