flask,中间键

from flask import Flask,request,render_template

app = Flask(__name__)

# @app.before_request
# def befor1():
# print(request)
# print("我是请求之前1")
# return "123"
# @app.before_request
# def befor2():
# print("我是请求之前2")

#
# @app.after_request
# def after1(response):
# print("我是请求之后1")
# return response
#
# @app.after_request
# def after2(response):
# print("我是请求之后2")
# return response

# @app.before_first_request
# def before_first():
# print("123")

#如论有没有异常都会执行，如果没有异常这个参数就是None，有就记录这个异常
# @app.teardown_request
# def tear(e):
# print('teardown_request')
# print(e)

#捕获异常，如果出现异常，而且状态就是@app.errorhandler(404),
@app.errorhandler(404)
def error_404(arg):
print(arg)
return "404错误了"

# @app.errorhandler(500)
# def error(arg):
# print(arg)
# return "500错误了"