后端框架flask学习小记[通俗易懂]

pip install flask

from flask import Flask
app = Flask(__name__)

@app.route('/')   # 这个根目录，就是127.0.0.1:5000进入的位置
def hello_world():
	return "hello world"

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

app.run(host, port, debug, options)

# 允许服务器被公开访问
app.run(debug=True, host='0.0.0.0', port=3000, threaded=True)
# 只能被自己的机子访问
# app.run(debug=True, host='127.0.0.1', port=10086, threaded=True)

# 通过装饰器的方式， Flask框架会将URL规则绑定到test()函数上， 这个很好用
@app.route('/test')       # 浏览器访问的时候，输入的url是127.0.0.1/test
def test():
	return 'this is response of test function'

def test():
  return 'this is response of test function.'
app.add_url_rule('/test',view_func=test)

# 接收post和get请求， 如果不指定的话，就是get请求， 此时如果提交post请求是捕捉不到的
@app.route('/user', methods = ['POST', 'GET'])   
def get_users():
  if request.method == 'GET':
    return ... # 返回用户列表
  else:
    return ... # 创建新用户

@app.route('/user/<uname>')   # <>提取参数用的
def get_userInfo(uname):
  return '%s\'s Informations' % uname


# 输入网址127.0.0.1/user/wuzhongqiang wuzhongqiang's Informations
# 输入网址127.0.0.1/user/zhangsan zhangsan's Informations

@app.route('/user/<int:uname>')   # <int: name> int 是一个转换器
def get_userInfo(uname):
    return '%s\'s Informations' % uname

@app.route('/user')
@app.route('/user/<uname>')
@app.route('/user/<int:uname>')
def get_userInfo(uname=None):
    if uname:
    	return '%s\'s Informations' % uname
    else:
        return 'this is all informations of users'

from flask import Flask
from werkzeug.routing import BaseConverter

app = Flask(__name__)

class RegexConverter(BaseConverter):
    """自定义转化器类"""
    def __init__(self, url_map, regex):
        super(RegexConverter, self).__init__(url_map)
        self.regex = regex

    def to_python(self, value: str):
        return value

# 将自定义的转换器类添加到flask应用中
app.url_map.converters['re'] = RegexConverter

@app.route('/index/<re("1\d{5}"):value>')   
def index(value):
    return "hello, world"

app.run()

# 只有如输入 127.0.0.1/index/123456 1开头，后面5位整数的才能匹配到

@app.route('/')
def hello():
    return 'Hello world!'
    
@app.route('/test')
def test_url_for():
    print(url_for('hello'))  # 跳转到了hello函数下面执行

from flask import request, session, make_response

@app.route('/login', methods=['POST', 'GET'])
def logion():
	if request.method == 'POST':
		if request.form['username'] == 'admin':
			session['username'] = request.form['username']
			response = make_response('Admin login successfully!')
			response.set_cookie('login_time', time.strftime('%Y-%m-%d' %H:%M:%S'))
			return 'Admin login successfully!'
	elif request.method == 'GET':
		if request.args.get("username") == 'admin':
            session['username'] = request.form['username']
            return 'Admin login successfully!'
    else:
            return 'No such user!'

app.secret_key = '123456'

from flask import Flask, jsonify, request
@app.route('/login', methods=["POST"])
def login():
    request_str = request.get_data()
    request_dict = json.loads(request_str)
    # 然后，就可以对request_dict进行处理了，相当于从后端拿到了前端的数据

@app.route("/user_one")
def user_one():
    return "userInfo.html", "200 Ok", { 
     "name": "zhangsan"; "age":"20"}

from flask import Response

@app.route("/user_one")
def user_one():
    response = Response("user_one")
    response.status_code = 200
    response.status = "200 ok"
    response.data = { 
     "name": "zhangsan"; "age":"20"}
    return response

from flask import Flask, redirect, url_for

app = Flask(__name__)

@app.route("/demo")
def demo():
    url = url_for("demo2")  # 路由反转，根据视图函数名获取路由地址
    return redirect(url)   # 相当于到了/demo2这个页面，显式this is demo2 page

@app.route("/demo2")
def demo2():
    return "this is demo2 page"

@app.route("/")
def index():
    # 使用方法：redirect(location, code=302, Response=None) 
    return redirect("/demo", 301)

from flask import render_template   # 渲染页面

@app.errorhandler(404)
def page_not_found(error):
    return render_template('page_not_found.html'), 404

from flask import abort
@app.route('/index', methods=['GET', 'POST'])
def index():
		if request.method == 'GET':
				return render_template('index.html')
		if request.method == 'POST':
				name = request.form.get('name')
				password = request.form.get('password')
				if name == 'zhangsan' and password == '123':
								return 'login success'
				else:
								abort(404)
								return None

from flask import Flask, render_template

app = Flask(__name__)

@app.route('/index')
def index():
    return render_template('index.html')  # 渲染当前的html页面

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

# 输入127.0.0.1:5000/index 就会出来写的那个html页面了，然后输入密码，提交，就会得到一个get请求

from flask import Flask, render_template
from flask import request

app = Flask(__name__)

@app.route('/index', methods=['GET', 'POST'])
def index():
    if request.method == 'GET':
        # 渲染index页面
        return render_template('index.html')
    elif request.method == 'POST':
        # 获取数据
        data = { 
   }
        data['name'] = request.args.get('name')   # 后面这个name和前端的name保持一致
        data['passwd'] = request.args.get('password')

        # 返回到前端去
        return render_template('index2.html', data=data)

    return render_template('index.html')

app.run()

# 安装
pip install SQLalchemy

from sqlalchemy import create_engine

def mysql_db(host='127.0.0.1', dbname='3306'):
	engine = create_engine("mysql+pymysql://root:123456@{}:49168/{}?charset=utf8".formate(host, dbname))
	print(engine) # Engine(mysql+pymysql://root:***@127.0.0.1:49168/3306?charset=utf8)

create_engine("mysql://user:password@hostname/dbname?charset=utf8",
                       echo=True,
                       pool_size=8,
                       pool_recycle=60*30)

from sqlalchemy import create_engine, Column, Integer, String
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()

class User(Base):
	__tablename__ = 'UserInfo'  # 表名
	# 数据库字段的类型
	index = Column(Integer(), primary_key=True)
	user_id = Column(Integer(), unique=True)
	username = Column(String(30))
	passwd = Column(String(500))

	def __init__(self, index, user_id, username, passwd):
		self.index = index
		self.user_id = user_id
		self.username = username
		self.paswd = passwd

def mysql_db(host='127.0.0.1', dbname='test'):
	engine = create("mysql+pymysql://root:123456@{}:49168/{}?charset=utf8mb4".format(host,dbname))
	
	session = sessionmaker(bind=engine)
	Base.metadata.create_all(engine)
	return engine, session()

# 增加一个用户
engine, session = mysql_db()

user = User("100", "zhangsan", "11111")
session.add(user)
session.commit()

# 也可以通过addall批量提交
engine, session = mysql_db()
user1 = User("101","lisi","11111")
user2 = User("102","wangwu","22222")
session.add_all([user1,user2])
session.commit()

engine, session = mysql_db()
users = session.query(User).filter_by(passwd='11111').all()

for item in users:
    print(item.username,item.passwd)

session.query(User).filter_by(username="zhangsan").update({ 
     'passwd': "123456"})

session.query(User).filter(User.username == "zhangsan-test").delete()
session.commit()

@app.route('/recsys/register', methods=["POST"])
def register():
    """用户注册 """
    request_str = request.get_data()
    request_dict = json.loads(request_str)
    print(request_dict)

    user = RegisterUser()
    user.username = request_dict["username"]
    user.passwd = request_dict["passwd"]

    # 查询当前用户名是否已经被用过了
    result = UserAction().user_is_exist(user, "register")

    if result != 0:
        return jsonify({ 
   "code": 500, "mgs": "this username is exists"})

    #user.userid = snowflake.client.get_guid() # 雪花算法
    user.userid = 20211971672
    user.age = request_dict["age"]
    user.gender = request_dict["gender"]
    user.city = request_dict["city"]
    print("hello world")

    # 添加注册用户
    save_res = UserAction().save_user(user)
    if not save_res:
        return jsonify({ 
   "code": 500, "mgs": "register fail."})

    return jsonify({ 
   "code": 200, "msg": "register success."})

# 命令行输入
echo fs.inotify.max_user_watches=524288 | sudo tee -a /etc/sysctl.conf && sudo sysctl -p