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，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。

flask是一个微框架，短小精悍，只保留核心的功能，可拓展性极强。

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。

Werkzeug模块使用实例

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

from flask import Flask
app = Flask(__name__)

@app.route('/')
def hello():
    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
     ...
    }

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， 内部调用from_pyfile方法

    app.config.from_json("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'L: 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    

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'

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)　　　　　　　　　　　　　　　　　　

　　

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'])

 

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()

from flask import Flask

# 实例化Flask对象
app = Flask(__name__)

def index():
    return "index"

app.add_url_route('/xxxx', "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()

一旦我们使用了endpoint参数，我们在使用url_for()反转的时候就不能使用视图函数的函数名了，而是要用我们定义的url名（就是endpoint传入的名字）

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参数相当于fbv的endpoint

3.@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

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()

 

五、模板

Flask使用的事Jinja2模板，所以和Django模板语法差不多。

自定义模板方法

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()
def sb(a1,a2):
    return a1 + a2 + 100


@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' />")
    return render_template('index.html',v1=v1,v2=v2,v3=v3,v4=v4,test=test)


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

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
    <h1>模板</h1>
    {%block body %} {%endblock%}

</body>
</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%}

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()

模仿django的request.GET.urlencode

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()

 

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

• 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">
            <input type=text name=username>
            <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'))

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()

 

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()

 

九、扩展（类似于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()

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)

 

十、蓝图

目录结构

 

 

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'

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

来源：https://www.cnblogs.com/Xuuuuuu/p/12070087.html