flask基础入门

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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`

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

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")

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一下对应关系来处理：

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()

a.注册路由原理

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=''))
return 'Index' if __name__ == '__main__':
app.run()

b. 自定制正则路由匹配

四、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>

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

<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Title</title>
</head>
<body> {% macro input(name, type='text', value='') %}
<input type="{{ type }}" name="{{ name }}" value="{{ value }}">
{% endmacro %} {{ input('n1') }} {% include 'tp.html' %} <h1>asdf{{ v.k1}}</h1>
</body>
</html>

其他

注意：Markup等价django的mark_safe

五、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()

六、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)

from flask import Flask, session, redirect, url_for, escape, requestapp = Flask(__name__)@app.route('/')
def index():
if 'username' in session:
return 'Logged in as %s' % escape(session['username'])
return 'You are not logged in'@app.route('/login', methods=['GET', 'POST'])
def login():
if request.method == 'POST':
session['username'] = request.form['username']
return redirect(url_for('index'))
return '''
<form action="" method="post">
<p><input type=text name=username>
<p><input type=submit value=Login>
</form>
'''@app.route('/logout')
def logout():
# remove the username from the session if it's 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

pip3 install Flask-Session run.py
from flask import Flask
from flask import session
from pro_flask.utils.session import MySessionInterface
app = Flask(__name__) app.secret_key = 'A0Zr98j/3yX R~XHH!jmN]LWX/,?RT'
app.session_interface = MySessionInterface() @app.route('/login.html', methods=['GET', "POST"])
def login():
print(session)
session['user1'] = 'alex'
session['user2'] = 'alex'
del session['user2'] return "内容" if __name__ == '__main__':
app.run() session.py
#!/usr/bin/env python
# -*- coding:utf-8 -*-
import uuid
import json
from flask.sessions import SessionInterface
from flask.sessions import SessionMixin
from itsdangerous import Signer, BadSignature, want_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 = {} def __init__(self):
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:
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)

自定义Session

#!/usr/bin/env python
# -*- coding:utf-8 -*-
"""
pip3 install redis
pip3 install flask-session"""from flask import Flask, session, redirect
from flask.ext.session import Sessionapp = Flask(__name__)
app.debug = True
app.secret_key = 'asdfasdfasd'app.config['SESSION_TYPE'] = 'redis'
from redis import Redis
app.config['SESSION_REDIS'] = Redis(host='192.168.0.94',port='')
Session(app)@app.route('/login')
def login():
session['username'] = 'alex'
return redirect('/index')@app.route('/index')
def index():
name = session['username']
return nameif __name__ == '__main__':
app.run()

第三方session

七、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('account', __name__,url_prefix='/xxx')
蓝图子域名：xxx = Blueprint('account', __name__,subdomain='admin')
# 前提需要给配置SERVER_NAME： app.config['SERVER_NAME'] = 'wupeiqi.com:5000'
# 访问时：admin.wupeiqi.com:5000/login.html

八、message

message是一个基于Session实现的用于保存数据的集合，其特点是：使用一次就删除。

from flask import Flask, flash, redirect, render_template, request, get_flashed_messages app = Flask(__name__)
app.secret_key = 'some_secret' @app.route('/')
def index1():
messages = get_flashed_messages()
print(messages)
return "Index1" @app.route('/set')
def index2():
v = request.args.get('p')
flash(v)
return 'ok' if __name__ == "__main__":
app.run()

九、中间件

from flask import Flask, flash, redirect, render_template, requestapp = Flask(__name__)
app.secret_key = 'some_secret'@app.route('/')
def index1():
return render_template('index.html')@app.route('/set')
def index2():
v = request.args.get('p')
flash(v)
return 'ok'class MiddleWare:
def __init__(self,wsgi_app):
self.wsgi_app = wsgi_app def __call__(self, *args, **kwargs): return self.wsgi_app(*args, **kwargs)if __name__ == "__main__":
app.wsgi_app = MiddleWare(app.wsgi_app)
app.run(port=9999)

十、请求扩展

#!/usr/bin/env python
# -*- coding:utf-8 -*-
from flask import Flask, Request, render_templateapp = Flask(__name__, template_folder='templates')
app.debug = True@app.before_first_request
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()