I have the following code snippet, I marked my question in a comment line
inside the hybrid_property.expression part. As you can see, it is now not
implemented:
from sqlalchemy.ext.declarative import declared_attr
from sqlalchemy import Column, Integer, String, Unicode, UnicodeText
from sqlalchemy.ext.hybrid import hybrid_property, hybrid_method
import arrow
datetimeString_format = {
"UTC": "%Y-%m-%d %H:%M:%S+00:00",
"local_with_timezoneMarker": "%Y-%m-%d %H:%M:%S %Z",
"local_without_timezoneMarker": "%Y-%m-%d %H:%M:%S"
}
dateString_format = "%Y-%m-%d"
class My_TimePoint_Mixin:
# define output formats:
datetimeString_inUTC_format = "%Y-%m-%d %H:%M:%S+00:00"
datetimeString_naive_format = "%Y-%m-%d %H:%M:%S"
# instrumented fields:
_TimePoint_in_database = Column('timepoint', String, nullable=False)
_TimePoint_in_database_suffix = Column(
'timepoint_suffix', String, nullable=False)
@hybrid_property
def timepoint(self):
twoPossibleType_handlers = [
self._report_ACCRT_DATE,
self._report_ACCRT_DATETIME
]
for handler in twoPossibleType_handlers:
print("handler: ", handler)
try:
return handler(self)
except (AssertionError, ValueError) as e:
logging.warning("Try next handler!")
@timepoint.expression
def timepoint(cls):
pass
# How can I implement SQL expression for a equivalent function
dispatch here? There seems to be no SQL equivalent structure for this?
@timepoint.setter
def timepoint(self, datetimepointOBJ):
handlers_lookup = {
datetime.datetime: self._set_ACCRT_DATETIME,
datetime.date: self._set_ACCRT_DATE
}
this_time = type(datetimepointOBJ)
this_handler = handlers_lookup[this_time]
print("handler: ", this_handler)
this_handler(datetimepointOBJ)
def _report_ACCRT_DATE(self):
"""Accurate Date"""
assert self._TimePoint_in_database_suffix == "ACCRT_DATE"
date_string = self._TimePoint_in_database
dateString_format = "%Y-%m-%d"
# return a datetime.date
return datetime.datetime.strptime(date_string, dateString_format).
date()
def _report_ACCRT_DATETIME(self):
"""Accurate DateTime"""
assert self._TimePoint_in_database_suffix in pytz.all_timezones_set
datetimeString_inUTC = self._TimePoint_in_database
utc_naive = datetime.datetime.strptime(
datetimeString_inUTC, self.datetimeString_inUTC_format)
utc_timepoint = arrow.get(utc_naive, "utc")
# localize
local_timepoint = utc_timepoint.to(self.
_TimePoint_in_database_suffix)
# return a datetime.datetime
return local_timepoint.datetime
def _set_ACCRT_DATETIME(self, datetimeOBJ_aware):
assert isinstance(datetimeOBJ_aware, datetime.datetime), "Must be a
valid datetime.datetime!"
assert datetimeOBJ_aware.tzinfo is not None, "Must contain tzinfo!"
utctime_aware_arrow = arrow.get(datetimeOBJ_aware).to('utc')
utctime_aware_datetime = utctime_aware_arrow.datetime
store_datetime_string = utctime_aware_datetime.strftime(
self.datetimeString_inUTC_format)
self._TimePoint_in_database = store_datetime_string
def _set_ACCRT_DATE(self, dateOBJ):
store_date_string = dateOBJ.isoformat()
self._TimePoint_in_database = store_date_string
Could someone please point out a clue as to implement the
hybrid_property.expression part? Thanks.
I've also posted a similar issue on stackoverflow.com, for reference:
http://stackoverflow.com/questions/39485440/calling-from-the-same-class-why-is-one-treated-as-bound-method-while-the-other
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