python学习之__format__

定制__format__方法

format_dic={
'ymd':'{0.year}{0.mon}{0.day}',
'm-d-y':'{0.mon}-{0.day}-{0.year}',
'y:m:d':'{0.year}:{0.mon}:{0.day}'
}
class Date:
def __init__(self,year,mon,day):
self.year=year
self.mon=mon
self.day=day
def __format__(self, format_spec):
print('我执行啦')
print('--->',format_spec)
if not format_spec or format_spec not in format_dic:
format_spec='ymd'
fm=format_dic[format_spec]
return fm.format(self)
d1=Date(2016,12,26)
# format(d1) #d1.__format__()
# print(format(d1))
print(format(d1,'ymd'))
print(format(d1,'y:m:d'))
print(format(d1,'m-d-y'))
print(format(d1,'m-d:y'))
print('===========>',format(d1,'asdfasdfsadfasdfasdfasdfasdfasdfasdfasdfasdfasdfasd'))