Flask知识点整理
文章目录
- 1.URL与视图的映射
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- 带参数的url：将参数固定到了path中
- 查询字符串的方式传参
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- 2.模板渲染
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- 给html文件传参
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- 3.模板访问对象属性
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- User 是个类
- User是个字典
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- 4.过滤器的使用
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- 通过一个 | 管道符进行过滤
- 自定义过滤器
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- 5.控制语句
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- if
- for
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- 6.Flask连接MySQL数据库
- 7.ORM模型与表的映射
- 8.ORM模型的CRUD操作
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- create
- query
- update
- delete
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- 9.flask-migrate迁移ORM模型
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- ORM模型映射成表的三步
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- 1.flask db init 这步只需要执行一次
- 2.flask db migrate 识别ORM模型的改变，生成迁移脚本
- 3.flask db upgrade 运行迁移脚本，同步到数据库中
1.URL与视图的映射
带参数的url：将参数固定到了path中
from flask import Flask
app = Flask(__name__)
@app.route('/blog/' )
def blog_detail(blog_id):
return "访问的是:%s"% blog_id
查询字符串的方式传参
from flask import Flask ， request
@app.route('/book/list')
def book_list():
page = request.args.get("page",default = 1,type = int)
return f"您获取的是第{page}的图书列表！"
http://127.0.0.1:5000/book/list?page=5
2.模板渲染
给html文件传参
from flask import Flask,render_template
@app.route('/blog/' )
def blog_detail(blog_id):
return render_template("blog_detail.html",blog_id,username = "krien")
<body>
<p> 您的用户名是 {{ username }}p>
<h1>您访问的博客详情是:{{ blog_id }}h1>
<body>
3.模板访问对象属性
User 是个类
class User:
def __init__(self,username,email):
self.username = username
self.email = email
@app.route('/')
def hello_world(): # put application's code here
user = User(username = "krien", email = "[email protected]")
return render_template('index.html',user = user)
<body>
{{ user.username }} / {{ user.email }}
<body>
User是个字典
from flask import Flask,render_template ,request
app = Flask(__name__)
@app.route('/')
def hello_world(): # put application's code here
user = User(username = "krien", email = "[email protected]")
person = {
"username":"张三",
"email":"[email protected]"
}
return render_template('index.html',user = user,person = person)
<body>
<div> {{ user.username }} / {{ user.email }} div>
<div> {{ person.username}} / {{ person.email }} div>
<body>
4.过滤器的使用
通过一个 | 管道符进行过滤
from flask import Flask,render_template ,request
from flask import Flask,render_template ,request
@app.route('/filter')
def filter_demo(): # put application's code here
user = User(username = "krien", email = "[email protected]")
return render_template('filter.html',user = user)
<body>
{{ user.username }}-{{ user.username|length }}
<body>
自定义过滤器
过滤器本质上是一个 Python 函数，他会把过滤的值当作第一个参数传给这个函数，函数经过一些逻辑处理后，在返回新的值。在过滤器函数写好之后，可以通过@app.template_filter装饰器或者是 app.add_template_filter 函数来把函数注册成Jinjia2 能用的过滤器
from flask import Flask,render_template ,request
from datetime import datetime
app = Flask(__name__)
def datetime_format(value,format = "%Y年%m月%d日 %H:%M"):
return value,strftime(format)
app.add_template_filter(datetime_format,"dformat")
@app.route('/filter')
def filter_demo(): # put application's code here
user = User(username = "krien", email = "[email protected]")
mytime = date_time.now()
return render_template('filter.html',user = user,mytime = mytime)
<body>
{{ user.username }}-{{ user.username|length }}
<div> {{mytime|dformat}} div>
<body>
5.控制语句
if
@app.route("/control")
def control_statement():
age = 17
return render_template("control.html",age=age)
<body>
{{% if age>18 %}}
<div>您已经满18，可以进入网吧div>
{{% elif age==18 %}}
<div>您刚满18，需要父母陪同div>
{{% else %}}
<div>您未满18，不能进去div>
{{% endif %}}
<body>
for
{{% for book in books %}}
<div>图书名称：{{ book.name }},图书作者：{{ book.auther }}div>
{{% endfor %}}
6.Flask连接MySQL数据库
from sqlalchemy import text
app = Flask(__name__)
HOSTNAME = 'localhost'
PORT = 3306
USERNAME = "root"
PASSWORD = "123456"
DATABASE = "database_learn"
app.config['SQLALCHEMY_DATABASE_URI'] = f"mysql+pymysql://{USERNAME}:{PASSWORD}@{HOSTNAME}/{DATABASE}"
db = SQLAlchemy(app)
with app.app_context():
with db.engine.connect() as conn:
rs = conn.execute(text("select 1"))
print(rs.fetchone())
7.ORM模型与表的映射
class User(db.Model):
__tablename__ = 'user'
id = db.Column(db.Integer,primary_key = True,autoincrement = True)
username = db.Column(db.String(100),nullable = False)
password = db.Column(db.String(100),nullable = False)
with app.app_context():
db.create_all()
8.ORM模型的CRUD操作
create
@app.route('/user/add')
def add_user():
user = User(username="krien",password = '123456')
user1 = User(username='ddd',password = '121212')
db.session.add(user)
db.session.commit()
return "用户创建成功"
query
@app.route('/user/query')
def query_user():
# 1.get
user = User.query.get(1)
print(f"{user.id}:{user.username}-{user.password}")
# 2.filter_by 查找
return "数据查找成功"
update
@app.route('/user/update')
def update_user():
user = User.query.filter_by(username = "krien").first()
user.password = '222222'
db.session.commit()
return "数据更新成功"
delete
@app.route('/user/delete')
def delete_user():
user = User.query.get(2)
db.session.delete(user)
db.session.commit()
return "数据删除成功"