类初始化的多种方式

1.直接__init__

import time


class Date:
    def __init__(self, year, month, day):
        self.year = year
        self.month = month
        self.day = day
Date(2019,4,30)

2.使用类方法实例化

class Date:
    def __init__(self, year, month, day):
        self.year = year
        self.month = month
        self.day = day

    @classmethod
    def today(cls):
        t = time.localtime()

        return cls(t.tm_year, t.tm_mon, t.tm_yday)
d = Date.today()
print(d.year)

3.使用__new__

class Date:
    def __init__(self, year, month, day):
        self.year = year
        self.month = month
        self.day = day
d = Date.__new__(Date)
print(d)
for key, value in data.items(): #设置属性
    setattr(d, key, value)
print(d.year)

4.越过__init__方法实例化

class Date:
   def today2(cls):
        t =time.localtime()
        obj = cls.__new__(cls)
        setattr(obj,'year',t.tm_year)
        setattr(obj,'month',t.tm_mon)
        setattr(obj,"day",t.tm_yday)
        return obj
date = Date.today2()
print(date.year)