Refuse the temptation to pass

This is an opinion I sometimes remember when seeing some code. Don't take it as a strong advice, or a rule, but instead as a general guideline that might help you to improve the code slightly.

On this post I will share a tiny and opinionated argument about why there are usually better things to do in the code instead of just pass.

Disclaimer: I am not saying that pass should be banned from the language, or that is an anti-pattern, or a bad idiom. Nothing like that. If that were the case, it wouldn't be a keyword (and we know how few keywords Python has, and how hard it is to introduce a new one, so it's there for a good reason).

However, what I do argue, is that some of the nice features of Python are often over-used, and the temptation to abuse a nice feature shadows better opportunities.

For example, when defining exceptions:

class DataValidationError(Exception):
    pass

It's better to place a docstring explaining its raison d'etre, which eliminates the necessity for the pass and the empty body:

class DataValidationError(Exception):
    """A client error (400) when wrong data was provided."""

This also complies with the general good practice of "use docstrings in every function, class, and module defined". In my opinion, it's a much better choice.

The same criteria applies for empty base classes.

How about when dealing with exceptions?

Sometimes, the occurrence of an exception is a controlled scenario, and again pass looks really tempting:

try:
    custom_parsing(data)
except AttributeError:
    pass  # data is already parsed

Here the worst part is not even the pass, but the comment! Yes, comments represent our failure to express our ideas into code, and they are therefore, bad. We can cheat a little bit here, but (on the bright side), do something more useful: How about logging the message?

try:
    custom_parsing(data)
except AttributeError:
    logger.debug("data is already parsed")

If all of this seems unnecessary, we can suppress the exception:

with contextlib.suppress(AttributeError):
    custom_parsing(data)

There are lots of cases like this when using the keyword pass seems like a viable option. And again, I'm not saying it's a bad choice. I'm only inviting you to think more about it, and try to find a better alternative.