Flask基础知识

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。

Werkzeug的本质是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（虽然可以这么做），也不意味着Flask在功能上有所欠缺。

微型框架中“微”旨在保持核心简单而易于扩展。

Flask不会帮你做出太多决策——比如使用何种数据库。而那些Flask所选择的——比如使用何种引擎则很容易替换，除此之外的一切都由你掌握。

默认情况下，Flask不包含数据库抽象层、表单验证，或者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Flask本身实现的一样。

众多扩展提供了数据库集成、表单验证、上传处理、各种各样的开放验证技术等功能。

安装Flask：

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

#这部分的代码其实在flask内部已经帮你完成了

Werkzeug

一、基本使用

from flask import Flask
app = Flask(__name__)
 
@app.route('/')  #路由
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

配置文件整理

外部文件中：k=v k要大写

# NAME='ctz'
# PWD='123'



class BaseConfig(object):
    AA=123456


class TestConfig(BaseConfig):
    DB='127.0.0.1'

class DevConfig(BaseConfig):
    DB='127.0.0.2'

class ProConfig(BaseConfig):
    DB='1270.0.0.3'

View Code

from  flask import Flask
import settings
app=Flask(__name__)
#方式一
#app.config['COOK']='ctz'

'''
settings.py
NAME='ctz'
PWD='123'
'''
#方式二
#app.config.from_pyfile('settings.py')
#方式三
# import os
# os.environ['FLASK_SETTING']='settings.py'
# app.config.from_envvar('FLASK_SETTING')
#方式四(推荐使用)
app.config.from_object('settings.DevConfig')




@app.route('/index',methods=['POST','GET'],strict_slashes=False)
def index():
    print(app.config)
    return 'helloworld'

if __name__ == '__main__':
    app.run(debug=True)

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，所有路由系统都是基于以下对应关系来处理：

DEFAULT_CONVERTERS = {
    'default':          UnicodeConverter,
    'string':           UnicodeConverter,
    'any':              AnyConverter,
    'path':             PathConverter,
    'int':              IntegerConverter,
    'float':            FloatConverter,
    'uuid':             UUIDConverter,
}

四、视图函数

1.FBV

from flask import Flask

# 实例化Flask对象
app = Flask(__name__)

# 生成路由关系，并把关系保存到某个地方,app对象的 url_map字段中
@app.route('/xxxx')  # @decorator
def index():
    return "Index"



if __name__ == '__main__':
    # 启动程序，监听用户请求
    # 一旦请求到来，执行 app.__call__方法
    # 封装用户请求
    # 进行路由匹配
    app.run()

方式一

from flask import Flask

# 实例化Flask对象
app = Flask(__name__)



def index():
    return "Index"

app.add_url_rule('/xxx', "n1", index)

if __name__ == '__main__':
    # 启动程序，监听用户请求
    # 一旦请求到来，执行 app.__call__方法
    # 封装用户请求
    # 进行路由匹配
    app.run()

方式二

from flask import Flask,render_template,request,redirect,session

app = Flask(__name__,template_folder='templates',static_url_path='/xxxxxx')

app.secret_key = "sdfasdfasdf3fsdf"


@app.route('/login',methods=['GET',"POST"])
def login():
    if request.method == 'GET':
        return render_template('login.html')
    else:
        user = request.form.get('user')
        pwd = request.form.get('pwd')
        if user == 'alex' and pwd == '123':
            session['user_info'] = user
            return redirect('/index')
        else:
            return render_template('login.html',msg='用户名或密码错误')
            # return render_template('login.html',**{'msg':'用户名或密码错误'})

@app.route('/index',methods=['GET'])
def index():
    if not session.get('user_info'):
        return redirect('/login')
    return "欢迎登录"

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

简单使用

2.CBV

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反向解析

View Code

[email protected]和app.add_url_rule参数说明

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()

View Code

4.自定义正则路由匹配

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()

View Code

5.和Django比较

Django：
            /index/    func
            
            /index/    IndexClass.as_view()
            
Flask:
    FBV:
        @app.route('/index',endpoint='xx')
        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'))

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

View Code

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：

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

@app.template_global()  #所有的文件中都可以使用的函数
def sb(a1,a2):
    return a1 + a2 + 100


@app.template_filter()    #所有的文件中都可以使用的函数
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' />")
    return render_template('index.html',v1=v1,v2=v2,v3=v3,v4=v4,test=test)


if __name__ == '__main__':
    # app.__call__
    app.run()

View Code

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <h1>模板</h1>
    {%block body %} {%endblock%}  #和Django的传参一样

</body>
</html>

layout.html

{% 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,函数得带()

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()

请求相关信息

from flask import Flask,url_for,request,redirect,render_template,jsonify,make_response
from urllib.parse import urlencode,quote,unquote
app = Flask(__name__)

@app.route('/index',endpoint='xx')
def index():
    from werkzeug.datastructures import ImmutableMultiDict
    #模仿django的request.urlencode
    # get_data = request.args
    # get_dict = get_data.to_dict()
    # get_dict['xx'] = '18'
    # url = urlencode(get_dict)
    # print(url)

    # print(request.query_string)
    # print(request.args)

    # val = "%E6%8A%8A%E5%87%A0%E4%B8%AA"
    # print(unquote(val))
    #
    # return "Index"

    # return "Index"
    # return redirect()
    # return render_template()
    # return jsonify(name='alex',age='18')

    response = make_response('xxxxx')
    response.headers['xxx'] = '123123'
    return response


if __name__ == '__main__':
    # app.__call__
    app.run()

模仿django的request.GET.urlencode

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)

方法和字典一样

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

from flask import Flask,session,Session
from urllib.parse import urlencode,quote,unquote
from werkzeug.local import LocalProxy
app = Flask(__name__)
app.secret_key ='sdfsdfsdf'
app.config['SESSION_COOKIE_NAME'] = 'session_lvning'
"""
'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,
'PERMANENT_SESSION_LIFETIME':           timedelta(days=31)
"""

@app.route('/index',endpoint='xx')
def index():
    # session本质上操作的是字典,假设session保存在数据库
    # session['xxx'] = 123
    # session['xx1'] = 123
    # session['xx2'] = 123
    # session['xx3'] = 123
    # del session['xx2']
    session['xx3'] = 123
    return "xxx"

if __name__ == '__main__':
    # app.__call__
    app.run()

View Code

八、闪现

闪现是基于session实现的，当然用session也可以实现闪现的方法，闪现和session的区别就是闪现用了一次后值就没有了

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()

闪现实例

九、扩展（类似与Django的中间件）

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()

View Code

import pymysql
from  urllib.parse import urlencode

from flask import Flask, render_template, request, session, redirect

from utils.pager import Pagination

app = Flask(__name__)
app.secret_key = 'ctz123'
app.config

class MysqlCon(object):
    @classmethod
    def getCon(cls):
        con = pymysql.connect(host="localhost", user="root", password="root", database="pro1", charset="utf8")
        return con


VALID_URL = ['/login', ]


@app.route('/')
def hello_world():
    return 'Hello World!'


@app.before_request
def peocess_request():
    user = session.get('user')
    if request.path in VALID_URL:
        return None
    if not user:
        return redirect('/login')


@app.route('/login', methods=['POST', 'GET'], strict_slashes=False)
def login():
    if request.method == 'GET':
        return render_template('login.html')
    else:
        username = request.form.get('username')
        pwd = request.form.get('pwd')
        con = MysqlCon.getCon()
        cursor = con.cursor(cursor=pymysql.cursors.DictCursor)

        sql_user = 'select * from userinfo where username=%s and pwd=%s'
        cursor.execute(sql_user, [username, pwd])
        cursor.close()
        con.close()
        user = cursor.fetchone()
        if user:
            session['user'] = {'username': username, 'pwd': pwd}
            return redirect('/userlist')
        else:
            return render_template('login.html', msg='用户名或密码错误')


@app.route('/userlist', methods=['POST', 'GET'], strict_slashes=False)
def userlist():
    con = MysqlCon.getCon()
    cursor = con.cursor(cursor=pymysql.cursors.DictCursor)
    sql_list = 'select * from userinfo'
    cursor.execute(sql_list)
    userlist = cursor.fetchall()
    current_page = request.args.get('page', 1)
    total_count = len(userlist)
    cursor.close()
    con.close()
    base_url = request.path

    parmas = request.args.to_dict()

    pageObj = Pagination(current_page, total_count, base_url, parmas)

    per_page_list = userlist[pageObj.start:pageObj.end]

    return render_template('list.html', userlist=per_page_list, pageObj=pageObj)


@app.route('/adduser', methods=['GET', 'POST'], strict_slashes=False)
def addUser():
    if request.method == 'GET':
        return render_template('addUser.html')
    else:
        username = request.form.get('username')

        pwd = request.form.get('pwd')

        age = request.form.get('age')

        email = request.form.get('email')
        print(username, pwd, age, email)
        con = MysqlCon.getCon()
        cursor = con.cursor(cursor=pymysql.cursors.DictCursor)

        sql = 'insert into userinfo(username,pwd,age,email)values(%s,%s,%s,%s)'
        cursor.execute(sql, [username, pwd, age, email])

        con.commit()
        cursor.close()
        con.close()
        return redirect('/userlist')


@app.route('/edituser/<int:sid>', methods=['GET', 'POST'])
def editUser(sid):
    if request.method == 'GET':
        con = MysqlCon.getCon()
        cursor = con.cursor(cursor=pymysql.cursors.DictCursor)
        sql = 'select * from userinfo where id=%s'
        cursor.execute(sql, [sid, ])
        user = cursor.fetchone()
        cursor.close()
        con.close()
        return render_template('editUser.html', user=user)
    else:
        parmars = urlencode(request.args.to_dict())
        con = MysqlCon.getCon()
        cursor = con.cursor(cursor=pymysql.cursors.DictCursor)

        username = request.form.get('username')

        pwd = request.form.get('pwd')

        age = request.form.get('age')

        email = request.form.get('email')

        sql = 'update userinfo set username=%s,pwd=%s,age=%s,email=%s where id=%s'
        cursor.execute(sql, [username, pwd, age, email, sid])

        con.commit()
        cursor.close()
        con.close()

        return redirect('%s?%s' % ('/userlist', parmars))


@app.route('/deluser/<int:sid>', methods=['POST', 'GET'])
def delUser(sid):
    con = MysqlCon.getCon()
    cursor = con.cursor(cursor=pymysql.cursors.DictCursor)
    sql = 'delete from userinfo where id=%s'
    cursor.execute(sql, [sid, ])
    con.commit()
    cursor.close()
    con.close()
    parmars = urlencode(request.args.to_dict())
    return redirect('%s?%s' % ('/userlist', parmars))


if __name__ == '__main__':
    app.run(debug=True)

扩展实例

十、蓝图

目录结构

from flask import Blueprint,render_template

account = Blueprint('account',__name__,)

@account.route('/login')
def login():
    # return 'Login'
    return render_template('login.html')

acount.py

from flask import Blueprint

order = Blueprint('order',__name__)

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

order.py

from flask import Flask
from .views import account
from .views import order

app = Flask(__name__)
print(app.root_path)
app.register_blueprint(account.account)
app.register_blueprint(order.order)

__init__.py

import fcrm

if __name__ == '__main__':
    fcrm.app.run(port=8001)

manage.py

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <h1>登录页面</h1>
</body>
</html>

更多信息查看Flask官方文档：http://docs.jinkan.org/docs/flask/index.html

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