python学习-70 自定制format

#  自定义format
dic_date = {
    'ymd':'{0.year}:{0.month}:{0.day}',
    'dmy':'{0.day}-{0.month}-{0.year}'
}
class Date:
    def __init__(self,year,month,day):
        self.year=year
        self.month=month
        self.day=day
    def __format__(self, format_spec):
        print('--->format_spec')
        if not format_spec or format_spec not in dic_date:
            print('please enter true time type')
            format_spec='ymd'           # 默认ymd格式的
        dd=dic_date[format_spec]
        return dd.format(self)

d1=Date(2019,11,11)
print(format(d1,'ymd'))

print(format(d1,'dmy'))

print(format(d1,'d-m-y'))

print(format(d1,'y.m.d'))

运行结果：

--->format_spec
2019:11:11
--->format_spec
11-11-2019
--->format_spec
please enter true time type
2019:11:11
--->format_spec
please enter true time type
2019:11:11

Process finished with exit code 0