I have a boolean field in the mysql db table.
# table model
class TestCase(Base):
__tablename__ = 'test_cases'
...
obsoleted = Column('obsoleted', Boolean)
To get the count of all the non-obsoleted test cases, that can be done simply like this:
caseNum = session.query(TestCase).filter(TestCase.obsoleted == False).count()
print(caseNum)
That works fine, but the flake8 report the following warning:
E712: Comparison to False should be "if cond is False:" or "if not cond:"
Okay, I think that make sense. So change my code to this:
caseNum = session.query(TestCase).filter(TestCase.obsoleted is False).count()
or
caseNum = session.query(TestCase).filter(not TestCase.obsoleted).count()
But neither of them can work. The result is always 0. I think the filter clause doesn't support the operator "is" or "is not". Will someone can tell me how to handle this situation. I don't want to disable the flake.
That's because SQLAlchemy filters are one of the few places where == False
actually makes sense. Everywhere else you should not use it.
Add a # noqa
comment to the line and be done with it.
Or you can use sqlalchemy.sql.expression.false
:
from sqlalchemy.sql.expression import false
TestCase.obsoleted == false()
where false()
returns the right value for your session SQL dialect. There is a matching sqlalchemy.expression.true
.
SQL Alchemy also has is_
and isnot
functions you can use. An example would be
Model.filter(Model.deleted.is_(False))
@Jruv Use # noqa
in front of statement, it'll ignore the warning.
来源:https://stackoverflow.com/questions/18998010/flake8-complains-on-boolean-comparison-in-filter-clause