我有以下型号
class MyModel(models.Model):
start = models.TimeField()
finish = models.TimeField()
penalty = models.IntegerField(blank=True, default=0) # penalty in minutes
以及管理员中的以下查询集注释
def get_queryset(self, request):
qs = super().get_queryset(request)
qs = qs.annotate(
total_time=ExpressionWrapper(
F("finish") - F("start") + F("penalty") * 60,
output_field=DurationField()
)
)
return qs
当我在penalty != 0
的一行中检查注解值时,会得到类似datetime.timedelta(0, 1800, 1800)
的信息(在这种情况下,罚款为30分钟)。
但是,我期望像datetime.timedelta(0, 3600)
这样的时间增量。有人可以解释吗?
我也尝试过
def get_queryset(self, request):
qs = super().get_queryset(request)
qs = qs.annotate(
duration=ExpressionWrapper(
F("finish") - F("start"),
output_field=DurationField()
)
)
qs = qs.annotate(
total_time=ExpressionWrapper(
F("duration") + F("route_shortening_penalty") * 60,
output_field=DurationField()
)
)
return qs
甚至
def get_queryset(self, request):
qs = super().get_queryset(request)
qs = qs.annotate(
duration=ExpressionWrapper(
F("finish") - F("start"),
output_field=DurationField()
),
penalty_duration=ExpressionWrapper(
F("penalty") * 60,
output_field=DurationField()
)
)
qs = qs.annotate(
total_time=ExpressionWrapper(
F("duration") + F("penalty_duration"),
output_field=DurationField()
)
)
return qs
两者都导致
Traceback (most recent call last):
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/core/handlers/exception.py", line 34, in inner
response = get_response(request)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/core/handlers/base.py", line 126, in _get_response
response = self.process_exception_by_middleware(e, request)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/core/handlers/base.py", line 124, in _get_response
response = wrapped_callback(request, *callback_args, **callback_kwargs)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/contrib/admin/options.py", line 604, in wrapper
return self.admin_site.admin_view(view)(*args, **kwargs)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/utils/decorators.py", line 142, in _wrapped_view
response = view_func(request, *args, **kwargs)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/views/decorators/cache.py", line 44, in _wrapped_view_func
response = view_func(request, *args, **kwargs)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/contrib/admin/sites.py", line 223, in inner
return view(request, *args, **kwargs)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/utils/decorators.py", line 45, in _wrapper
return bound_method(*args, **kwargs)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/utils/decorators.py", line 142, in _wrapped_view
response = view_func(request, *args, **kwargs)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/contrib/admin/options.py", line 1793, in changelist_view
'selection_note': _('0 of %(cnt)s selected') % {'cnt': len(cl.result_list)},
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/db/models/query.py", line 250, in __len__
self._fetch_all()
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/db/models/query.py", line 1186, in _fetch_all
self._result_cache = list(self._iterable_class(self))
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/db/models/query.py", line 63, in __iter__
for row in compiler.results_iter(results):
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/db/models/sql/compiler.py", line 1009, in apply_converters
value = converter(value, expression, connection)
File "/home/dm/.virtualenvs/test/lib/python3.6/site-packages/django/db/backends/base/operations.py", line 573, in convert_durationfield_value
return datetime.timedelta(0, 0, value)
TypeError: unsupported type for timedelta microseconds component: str
我正在使用Python 3.6.7
,Django==2.1.7
和SQLite version 3022000
。
答案 0 :(得分:1)
如果您得到datetime.timedelta(0, 1800, 1800)
而不是正确的datetime.timedelta(0, 3600)
,那么您显然快到了。
我假设1800秒是F("finish")
和F("start")
之间的差,而1800微秒来自F("penalty") * 60
。
乘以60*1000*1000
而不是60
,将penalty
从分钟转换为微秒:
total_time=ExpressionWrapper(
F("finish") - F("start") + F("penalty") * 60000000,
output_field=DurationField()
)