自定制format

 1 format_dic = {
 2     'y-m-d': '{0.year}-{0.mon}-{0.day}',
 3     'y:m:d': '{0.year}:{0.mon}:{0.day}',
 4     'dmy': '{0.day}{0.mon}{0.year}',
 5 }
 6 
 7 
 8 class Date:
 9     def __init__(self, year, mon, day):
10         self.year = year
11         self.mon = mon
12         self.day = day
13 
14     def __format__(self, format_spec):
15         if format_spec not in format_dic.keys() or not format_dic[format_spec]:
16             format_spec = 'y-m-d'
17         fm = format_dic[format_spec]
18         return fm.format(self)
19 
20 
21 d1 = Date(2020, 3, 8)
22 print(format(d1))
23 输出：
24 2020-3-8

自己定制format方法