flake8 抱怨布尔比较“=="；在过滤器子句中

2021-12-30 00:00:00 python sqlalchemy flake8 mysql

我在 mysql db 表中有一个布尔字段.

I have a boolean field in the mysql db table. 

# table model
class TestCase(Base):
    __tablename__ = 'test_cases'
    ...
    obsoleted = Column('obsoleted',  Boolean)

要获得所有未过时的测试用例的数量，可以简单地像这样完成:

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)

效果很好，但是 flake8 报告了以下警告:

That works fine, but the flake8 report the following warning:

E712:与 False 的比较应该是if cond is False:"或if not条件:"

E712: Comparison to False should be "if cond is False:" or "if not cond:"

好吧，我认为这是有道理的.所以把我的代码改成这样:

Okay, I think that make sense. So change my code to this:

caseNum = session.query(TestCase).filter(TestCase.obsoleted is False).count()

或 

caseNum = session.query(TestCase).filter(not TestCase.obsoleted).count()

但是它们都不能工作.结果始终为 0.我认为过滤器子句不支持运算符是"或不是".请问有人可以告诉我如何处理这种情况.我不想禁用薄片.

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.

推荐答案

那是因为 SQLAlchemy 过滤器是 == False 真正有意义的少数几个地方之一.其他地方你应该不要使用它.

That's because SQLAlchemy filters are one of the few places where == False actually makes sense. Everywhere else you should not use it.

在该行中添加 # noqa 注释并完成.

Add a # noqa comment to the line and be done with it.

或者你可以使用 sqlalchemy.sql.expression.false:

Or you can use sqlalchemy.sql.expression.false:

from sqlalchemy.sql.expression import false

TestCase.obsoleted == false()

where false() 返回会话 SQL 方言的正确值.有一个匹配的 sqlalchemy.expression.true.

where false() returns the right value for your session SQL dialect. There is a matching sqlalchemy.expression.true.

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