Flask學習之基礎知識與功能
一:flask的背景介紹
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,然後觸發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,並返回給使用者,如果要返回給使用者複雜的內容時,需要藉助jinja2模板來實現對模板的處理,即:將模板和資料進行渲染,將渲染後的字串返回給使用者瀏覽器。
“微”(micro) 並不表示你需要把整個 Web 應用塞進單個 Python 檔案(雖然確實可以 ),也不意味著 Flask 在功能上有所欠缺。微框架中的“微”意味著 Flask 旨在保持核心簡單而易於擴充套件。Flask 不會替你做出太多決策——比如使用何種資料庫。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。
預設情況下,Flask 不包含資料庫抽象層、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 支援用擴充套件來給應用新增這些功能,如同是 Flask 本身實現的一樣。眾多的擴充套件提供了資料庫整合、表單驗證、上傳處理、各種各樣的開放認證技術等功能。Flask 也許是“微小”的,但它已準備好在需求繁雜的生產環境中投入使用。
二:基本功能使用
1.補充:學習flask首先要了解裝飾器的使用方式
a:不帶引數的裝飾器
1 定義一個裝飾器函式: 2 def wrapper(func): 3 def inner(*args, **kwargs):View Code4 return func(*args, **kwargs) 5 return inner 6 7 用裝飾器wrapper函式裝飾index函式 8 @wrapper 9 def index(request): 10 pass 11 12 說明:執行@wrapper裝飾器等價於:index = wrapper(index),返回值是inner
b:帶引數的裝飾器
1 定義一個帶引數的裝飾器函式: 2 def route(option): 3 def inner(func,*args, **kwargs):View Code4 url_map[option['path']] = func 5 return inner 6 7 用route函式裝飾index函式,並傳入引數 8 @route({'path':'/index'}) 9 def index(request): 10 11 說明: 12 1.首先會執行route函式,將對應的引數{'path':'/index'}傳入,得到route函式的返回值inner 13 2.執行@inner等價於:inner = inner(index),此時:inner函式中的func = index;*args, **kwarg裡面的引數值等於我們傳入的值{'path':'/index'},因為是引數是字典的格式,因此是通過**kwargs傳入的。 14 3.執行url_map[option['path']] = func,等價於下面的路由關係 15 url_map = { 16 '/index': index 17 }
c:設定元資訊
1 mport functools 2 3 def wapper(func): 4 5 @functools.wraps(func) # 幫助我們設定函式的元資訊 6 def inner(*args,**kwargs): 7 return func(*args,**kwargs) 8 9 return inner 10 11 @wapper 12 def f1(): 13 pass 14 15 @wapper 16 def f2(): 17 pass 18 19 print(f1.__name__) 20 print(f2.__name__)View Code
2.三大python主流的框架對比:
Django:重武器,內部包含了非常多元件:ORM、Form、ModelForm、快取、Session、中介軟體、訊號等...
Flask:短小精悍,內部沒有太多元件。第三方元件非常豐富。路由比較特殊:基於裝飾器來實現,但是究其本質還是通過add_url_rule來實現。
Tornado:非同步非阻塞框架(node.js)
3.安裝:pip3 install flask
4.本質:Werkzeug WSGI
1 werkzeug示例: 2 from werkzeug.wrappers import Request, Response 3 @Request.application 4 def hello(request): 5 return Response('Hello World!') 6 7 if __name__ == '__main__': 8 from werkzeug.serving import run_simple 9 run_simple('localhost', 4000, hello) 10 11 wsgiref示例: 12 from wsgiref.simple_server import make_server 13 def runserver(environ, start_response): 14 start_response('200 OK', [('Content-Type', 'text/html')]) 15 return [bytes('<h1>Hello, web!</h1>',encoding='utf-8'), ] 16 17 if __name__ == '__main__': 18 # obj = WSGIHandler() 19 httpd = make_server('', 8000, runserver) 20 httpd.serve_forever()View Code
本質的本質:Werkzeug本質是Socket服務端
1 import socket 2 3 def handle_request(client): 4 buf = client.recv(1024) 5 client.send("HTTP/1.1 200 OK\r\n\r\n") 6 client.send("Hello, Seven") 7 8 def main(): 9 sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM) 10 sock.bind(('localhost',8000)) 11 sock.listen(5) 12 13 while True: 14 connection, address = sock.accept() 15 handle_request(connection) 16 connection.close() 17 18 if __name__ == '__main__': 19 main()View Code
5.基本使用
1 from flask import Flask 2 3 # 例項化Flask物件app 4 5 app = Flask(__name__) 6 7 # 設定路由關係 8 9 { 10 11 '/':index 12 13 } 14 15 @app.route("/") 16 17 def hello_world(): 18 return "hello world" 19 if __name__=="__main__": 20 app.run()View Code 6.配置檔案
1 flask中的配置檔案是一個flask.config.Config物件(繼承字典),預設配置為: 2 { 3 'DEBUG': get_debug_flag(default=False), 是否開啟Debug模式 4 'TESTING': False, 是否開啟測試模式 5 'PROPAGATE_EXCEPTIONS': None, 6 'PRESERVE_CONTEXT_ON_EXCEPTION': None, 7 'SECRET_KEY': None, 8 'PERMANENT_SESSION_LIFETIME': timedelta(days=31), 9 'USE_X_SENDFILE': False, 10 'LOGGER_NAME': None, 11 'LOGGER_HANDLER_POLICY': 'always', 12 'SERVER_NAME': None, 13 'APPLICATION_ROOT': None, 14 'SESSION_COOKIE_NAME': 'session', 15 'SESSION_COOKIE_DOMAIN': None, 16 'SESSION_COOKIE_PATH': None, 17 'SESSION_COOKIE_HTTPONLY': True, 18 'SESSION_COOKIE_SECURE': False, 19 'SESSION_REFRESH_EACH_REQUEST': True, 20 'MAX_CONTENT_LENGTH': None, 21 'SEND_FILE_MAX_AGE_DEFAULT': timedelta(hours=12), 22 'TRAP_BAD_REQUEST_ERRORS': False, 23 'TRAP_HTTP_EXCEPTIONS': False, 24 'EXPLAIN_TEMPLATE_LOADING': False, 25 'PREFERRED_URL_SCHEME': 'http', 26 'JSON_AS_ASCII': True, 27 'JSON_SORT_KEYS': True, 28 'JSONIFY_PRETTYPRINT_REGULAR': True, 29 'JSONIFY_MIMETYPE': 'application/json', 30 'TEMPLATES_AUTO_RELOAD': None, 31 } 32 33 方式一: 34 app.config['DEBUG'] = True 35 36 PS: 由於Config物件本質上是字典,所以還可以使用app.config.update(...) 37 38 方式二: 39 app.config.from_pyfile("python檔名稱") 40 如: 41 settings.py 42 DEBUG = True 43 44 app.config.from_pyfile("settings.py") 45 46 app.config.from_envvar("環境變數名稱") 47 環境變數的值為python檔名稱名稱,內部呼叫from_pyfile方法 48 49 50 app.config.from_json("json檔名稱") 51 JSON檔名稱,必須是json格式,因為內部會執行json.loads 52 53 app.config.from_mapping({'DEBUG':True}) 54 字典格式 55 56 一般的情況下使用物件的情況較多 57 app.config.from_object("python類或類的路徑") 58 59 app.config.from_object('pro_flask.settings.TestingConfig') 60 61 settings.py 62 63 class Config(object): 64 DEBUG = False 65 TESTING = False 66 DATABASE_URI = 'sqlite://:memory:' 67 68 class ProductionConfig(Config): 69 DATABASE_URI = 'mysql://[email protected]/foo' 70 71 class DevelopmentConfig(Config): 72 DEBUG = True 73 74 class TestingConfig(Config): 75 TESTING = True 76 77 PS: 從sys.path中已經存在路徑開始寫 78 79 80 PS: settings.py檔案預設路徑要放在程式root_path目錄,如果instance_relative_config為True,則就是instance_path目錄View Code 程式碼示例: 寫一個setting.py的檔案用來專案所需要的配置:
1 class Config(object): 2 DEBUG = False 3 TESTING = False 4 DATABASE_URI = 'sqlite://:memory:' 5 6 # 生產環境 7 class ProductionConfig(Config): 8 DATABASE_URI = 'mysql://[email protected]/foo' 9 10 #開發環境 11 class DevelopmentConfig(Config): 12 DEBUG = True 13 14 #測試環境 15 class TestingConfig(Config): 16 TESTING = TrueView Code
使用:
1 from flask import Flask 2 3 app = Flask(__name__) 4 app.debug = True 5 app.secret_key = "asdfasdf" 6 7 # 通過app.confgi.from_object 8 app.config.from_object("settings.DevelopmentConfig") 9 10 @app.route('/') 11 def index(): 12 return 'Hello World!' 13 14 if __name__ == '__main__': 15 app.run()View Code
7.路由系統
- @app.route('/user/<username>') # 帶字串的引數
- @app.route('/post/<int:post_id>')# 帶int型別的引數
- @app.route('/post/<float:post_id>')# 帶float型別的引數
- @app.route('/post/<path:path>')# 帶其他的路徑
- @app.route('/login', methods=['GET', 'POST']) # 帶提交請求的方式
a.路由的原始碼:
1 原始碼: 2 def route(self, rule, **options): 3 def decorator(f): 4 endpoint = options.pop('endpoint', None) 5 self.add_url_rule(rule, endpoint, f, **options) 6 return f 7 return decorator 8 9 說明:1.當檢視函式被app.route函式執行的時候,實際上檢視函式被route裝飾器裝飾,返回的值為decorator;相當於decorator = app.route('/',methods=['GET','POST'],endpoint='n1') 10 11 2.然後再執行@decorator,將引數傳進去View Code
b.示例程式碼:
1 from flask import Flask 2 3 app = Flask(__name__) 4 app.debug = True 5 app.secret_key = "asdfasdf" 6 7 """ 8 1. decorator = app.route('/',methods=['GET','POST'],endpoint='n1') 9 def route(self, rule, **options): 10 # self:app物件 11 # rule= / 12 # options = {methods=['GET','POST'],endpoint='n1'} 13 def decorator(f): 14 endpoint = options.pop('endpoint', None) 15 self.add_url_rule(rule, endpoint, f, **options) 16 return f 17 return decorator 18 2. @decorator 19 decorator(index) 20 """ 21 @app.route('/',methods=['GET','POST'],endpoint='n1') 22 def index(): 23 return 'Hello World!' 24 25 26 def login(): 27 return '登入' 28 29 app.add_url_rule('/login', 'n2', login, methods=['GET',"POST"]) 30 31 32 if __name__ == '__main__': 33 app.run()View Code
c.註冊路由的基本原理與路由用到的引數
1 1.基於CBV的路由: 2 def auth(func): 3 def inner(*args, **kwargs): 4 print('before') 5 result = func(*args, **kwargs) 6 print('after') 7 return result 8 9 return inner 10 11 class IndexView(views.View): 12 methods = ['GET'] 13 decorators = [auth, ] 14 15 def dispatch_request(self): 16 print('Index') 17 return 'Index!' 18 19 app.add_url_rule('/index', view_func=IndexView.as_view(name='index')) # name=endpoint 20 21 2.路由的基本引數: 22 @app.route和app.add_url_rule引數: 23 rule, URL規則 24 view_func, 檢視函式名稱 25 defaults=None, 預設值,當URL中無引數,函式需要引數時,使用defaults={'k':'v'}為函式提供引數 26 endpoint=None, 名稱,用於反向生成URL,即: url_for('名稱') 27 methods=None, 允許的請求方式,如:["GET","POST"] 28 29 30 strict_slashes=None, 對URL最後的 / 符號是否嚴格要求, 31 如: 32 @app.route('/index',strict_slashes=False), 33 訪問 http://www.xx.com/index/ 或 http://www.xx.com/index均可 34 @app.route('/index',strict_slashes=True) 35 僅訪問 http://www.xx.com/index 36 redirect_to=None, 重定向到指定地址 37 如: 38 @app.route('/index/<int:nid>', redirect_to='/home/<nid>') 39 或 40 def func(adapter, nid): 41 return "/home/888" 42 @app.route('/index/<int:nid>', redirect_to=func) 43 subdomain=None, 子域名訪問 44 from flask import Flask, views, url_for 45 46 app = Flask(import_name=__name__) 47 app.config['SERVER_NAME'] = 'wupeiqi.com:5000' 48 49 50 @app.route("/", subdomain="admin") 51 def static_index(): 52 """Flask supports static subdomains 53 This is available at static.your-domain.tld""" 54 return "static.your-domain.tld" 55 56 57 @app.route("/dynamic", subdomain="<username>") 58 def username_index(username): 59 """Dynamic subdomains are also supported 60 Try going to user1.your-domain.tld/dynamic""" 61 return username + ".your-domain.tld" 62 63 64 if __name__ == '__main__': 65 app.run() 66View Code
d.CVB示例程式碼:
1 from flask import Flask,views 2 3 app = Flask(__name__) 4 app.debug = True 5 app.secret_key = "asdfasdf" 6 7 8 def auth(func): 9 def inner(*args, **kwargs): 10 result = func(*args, **kwargs) 11 return result 12 return inner 13 14 class IndexView(views.MethodView): 15 methods = ['GET'] 16 decorators = [auth, ] 17 18 def get(self): 19 return 'Index.GET' 20 21 def post(self): 22 return 'Index.POST' 23 24 app.add_url_rule('/index', view_func=IndexView.as_view(name='index')) # name=endpoint 25 26 27 if __name__ == '__main__': 28 app.run()View Code
e.路由引數中redirect_to與defaults的示例程式碼:
1 from flask import Flask 2 3 app = Flask(__name__) 4 app.debug = True 5 app.secret_key = "asdfasdf" 6 7 8 # @app.route('/',methods=['GET','POST'],endpoint='n1',defaults={'nid':888}) 9 # def index(nid): 10 # print(nid) 11 # return 'Hello World!' 12 # 13 # 14 # def login(): 15 # return '登入' 16 # app.add_url_rule('/login', 'n2', login, methods=['GET',"POST"]) 17 18 19 @app.route('/index', methods=['GET', 'POST'], endpoint='n1', redirect_to="/index2") 20 def index(): 21 return '公司老首頁' 22 23 24 @app.route('/index2', methods=['GET', 'POST'], endpoint='n2') 25 def index2(): 26 return '公司新首頁' 27 28 29 if __name__ == '__main__': 30 app.run()View Code
f:路由引數中subdomain的示例程式碼:
1 from flask import Flask, views, url_for 2 3 app = Flask(import_name=__name__) 4 app.config['SERVER_NAME'] = 'chenjunkan.com:5000' 5 6 7 @app.route("/", subdomain="admin") 8 def static_index(): 9 """Flask supports static subdomains 10 This is available at static.your-domain.tld""" 11 return "xxxxxx.your-domain.tld" 12 13 14 @app.route("/dynamic", subdomain="<username>") 15 def username_index(username): 16 """Dynamic subdomains are also supported 17 Try going to user1.your-domain.tld/dynamic""" 18 return username + ".your-domain.tld" 19 20 21 if __name__ == '__main__': 22 app.run()View Code
g:自定義正則路由匹配
1 from flask import Flask, views, url_for 2 from werkzeug.routing import BaseConverter 3 4 app = Flask(import_name=__name__) 5 6 7 class RegexConverter(BaseConverter): 8 """ 9 自定義URL匹配正則表示式 10 """ 11 def __init__(self, map, regex): 12 super(RegexConverter, self).__init__(map) 13 self.regex = regex 14 15 def to_python(self, value): 16 """ 17 路由匹配時,匹配成功後傳遞給檢視函式中引數的值 18 :param value: 19 :return: 20 """ 21 return int(value) 22 23 def to_url(self, value): 24 """ 25 使用url_for反向生成URL時,傳遞的引數經過該方法處理,返回的值用於生成URL中的引數 26 :param value: 27 :return: 28 """ 29 val = super(RegexConverter, self).to_url(value) 30 return val 31 32 # 新增到flask中 33 app.url_map.converters['regex'] = RegexConverter 34 35 36 @app.route('/index/<regex("\d+"):nid>') 37 def index(nid): 38 print(url_for('index', nid='888')) 39 return 'Index' 40 41 42 if __name__ == '__main__': 43 app.run()View Code
8.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,建立一個函式並通過引數的形式傳入render_template
注意:Markup等價django的mark_safe
9.請求跟響應
1 from flask import Flask 2 from flask import request 3 from flask import render_template 4 from flask import redirect 5 from flask import make_response 6 7 app = Flask(__name__) 8 9 10 @app.route('/login.html', methods=['GET', "POST"]) 11 def login(): 12 13 # 請求相關資訊 14 # request.method 15 # request.args 16 # request.form 17 # request.values 18 # request.cookies 19 # request.headers 20 # request.path 21 # request.full_path 22 # request.script_root 23 # request.url 24 # request.base_url 25 # request.url_root 26 # request.host_url 27 # request.host 28 # request.files 29 # obj = request.files['the_file_name'] 30 # obj.save('/var/www/uploads/' + secure_filename(f.filename)) 31 32 # 響應相關資訊 33 # return "字串" 34 # return render_template('html模板路徑',**{}) 35 # return redirect('/index.html') 36 37 # response = make_response(render_template('index.html')) 38 # response是flask.wrappers.Response型別 39 # response.delete_cookie('key') 40 # response.set_cookie('key', 'value') 41 # response.headers['X-Something'] = 'A value' 42 # return response 43 44 45 return "內容" 46 47 if __name__ == '__main__': 48 app.run()View Code
10:session的使用
除請求物件之外,還有一個 session 物件。它允許你在不同請求間儲存特定使用者的資訊。它是在 Cookies 的基礎上實現的,並且對 Cookies 進行金鑰簽名要使用會話,你需要設定一個金鑰。
-
設定:session['username'] = 'xxx'
- 刪除:session.pop('username', None)
a.基本使用
1 from flask import Flask, session, redirect, url_for, escape, request 2 3 app = Flask(__name__) 4 5 @app.route('/') 6 def index(): 7 if 'username' in session: 8 return 'Logged in as %s' % escape(session['username']) 9 return 'You are not logged in' 10 11 @app.route('/login', methods=['GET', 'POST']) 12 def login(): 13 if request.method == 'POST': 14 session['username'] = request.form['username'] 15 return redirect(url_for('index')) 16 return ''' 17 <form action="" method="post"> 18 <p><input type=text name=username> 19 <p><input type=submit value=Login> 20 </form> 21 ''' 22 23 @app.route('/logout') 24 def logout(): 25 # remove the username from the session if it's there 26 session.pop('username', None) 27 return redirect(url_for('index')) 28 29 # set the secret key. keep this really secret: 30 app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'View Code
b.自定義session,後續的請求上下文中會詳細介紹Flask-Session
1 pip3 install Flask-Session 2 3 run.py 4 from flask import Flask 5 from flask import session 6 from pro_flask.utils.session import MySessionInterface 7 app = Flask(__name__) 8 9 app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT' 10 app.session_interface = MySessionInterface() 11 12 @app.route('/login.html', methods=['GET', "POST"]) 13 def login(): 14 print(session) 15 session['user1'] = 'alex' 16 session['user2'] = 'alex' 17 del session['user2'] 18 19 return "內容" 20 21 if __name__ == '__main__': 22 app.run() 23 24 session.py 25 #!/usr/bin/env python 26 # -*- coding:utf-8 -*- 27 import uuid 28 import json 29 from flask.sessions import SessionInterface 30 from flask.sessions import SessionMixin 31 from itsdangerous import Signer, BadSignature, want_bytes 32 33 34 class MySession(dict, SessionMixin): 35 def __init__(self, initial=None, sid=None): 36 self.sid = sid 37 self.initial = initial 38 super(MySession, self).__init__(initial or ()) 39 40 41 def __setitem__(self, key, value): 42 super(MySession, self).__setitem__(key, value) 43 44 def __getitem__(self, item): 45 return super(MySession, self).__getitem__(item) 46 47 def __delitem__(self, key): 48 super(MySession, self).__delitem__(key) 49 50 51 52 class MySessionInterface(SessionInterface): 53 session_class = MySession 54 container = {} 55 56 def __init__(self): 57 import redis 58 self.redis = redis.Redis() 59 60 def _generate_sid(self): 61 return str(uuid.uuid4()) 62 63 def _get_signer(self, app): 64 if not app.secret_key: 65 return None 66 return Signer(app.secret_key, salt='flask-session', 67 key_derivation='hmac') 68 69 def open_session(self, app, request): 70 """ 71 程式剛啟動時執行,需要返回一個session物件 72 """ 73 sid = request.cookies.get(app.session_cookie_name) 74 if not sid: 75 sid = self._generate_sid() 76 return self.session_class(sid=sid) 77 78 signer = self._get_signer(app) 79 try: 80 sid_as_bytes = signer.unsign(sid) 81 sid = sid_as_bytes.decode() 82 except BadSignature: 83 sid = self._generate_sid() 84 return self.session_class(sid=sid) 85 86 # session儲存在redis中 87 # val = self.redis.get(sid) 88 # session儲存在記憶體中 89 val = self.container.get(sid) 90 91 if val is not None: 92 try: 93 data = json.loads(val) 94 return self.session_class(data, sid=sid) 95 except: 96 return self.session_class(sid=sid) 97 return self.session_class(sid=sid) 98 99 def save_session(self, app, session, response): 100 """ 101 程式結束前執行,可以儲存session中所有的值 102 如: 103 儲存到resit 104 寫入到使用者cookie 105 """ 106 domain = self.get_cookie_domain(app) 107 path = self.get_cookie_path(app) 108 httponly = self.get_cookie_httponly(app) 109 secure = self.get_cookie_secure(app) 110 expires = self.get_expiration_time(app, session) 111 112 val = json.dumps(dict(session)) 113 114 # session儲存在redis中 115 # self.redis.setex(name=session.sid, value=val, time=app.permanent_session_lifetime) 116 # session儲存在記憶體中 117 self.container.setdefault(session.sid, val) 118 119 session_id = self._get_signer(app).sign(want_bytes(session.sid)) 120 121 response.set_cookie(app.session_cookie_name, session_id, 122 expires=expires, httponly=httponly, 123 domain=domain, path=path