Expressing IS NOT NULL without causing a PEP8 error

Question

At a certain point in my project, I need to query a SQLAlchemy object for columns that are NOT NULL. In my code, I do: ``` session.query(MyModel).filter(MyModel.my_column != None).all() ``` ...and it works great. Problem is, whenever I run `pep8` or one of the other linters on the file, it raises an error E711: Comparison to `None` should be `if cond is not None:`. I agree with the spirit of this guideline, and as such I don't want to silence the warning just because of one little line. Is there another way to write this? Preferably one where we don't have to dig into the `func` module?

Accepted Answer

PEP8 isn't meant to be followed to the letter.

You're recommended to use `is None` instead of `== None` because `is` cannot be overloaded (unlike `==`):

```
>>> class Bad(object):
...     def __eq__(self, other):
...         return True
...
>>> instance = Bad()
>>> instance == None
True
>>> instance is None
False
```

In your case you want to use the overloaded `==` operator, so the warning is incorrect.

There are three ways of making the warning go away:

You can disable that particular warning for that single line:

For Flake8/PyFlakes:

```
session.query(MyModel).filter(MyModel.my_column != None).all()  # noqa: E711
```

For Pylint:

```
session.query(MyModel).filter(MyModel.my_column != None).all()  # pylint: disable=singleton-comparison
```

You can avoid using the equality operator by directly calling the class's `__eq__` (for `==`) and `__ne__` (for `!=`) methods:

```
session.query(MyModel).filter(MyModel.my_column.__ne__(None)).all()
```

You can use `.is_` and `.isnot`:

```
session.query(MyModel).filter(MyModel.my_column.isnot(None)).all()
```

Note that `.is_` and `.isnot` are not the same as `==` and `!=`. `MyModel.my_column != x` can mean both `IS NOT NULL` and `!= x` depending on the value of `x` and your database, so solutions 1 and 2 are probably better unless you really don't like using `__`-methods and know the type of the right-hand-side of your expression.

Expressing IS NOT NULL without causing a PEP8 error

Solution

Problem