Technology

Apart from the quote from the zen of python, does this really make your code better though? You will end up writing 4-5 lines with an extra level of indentation. The code does the same, but has worse performance and communicates the intent poorly (compared to the “pythonic” version).

it's still implicit

I don't see it that way. If you're doing if len(foo) == 0, you're implying that foo is expected to not be None, and expecting an exception should not be the default assumption, because exceptions should be... exceptional.

Here's what I assume:

• if foo is not None - empty values are explicitly acceptable
• if not foo - the difference between an empty and None value isn't important
• if len(foo) == 0 - implicit assumption that foo is not None (I frequently forget that len(...) raises on None)

If an exception was intended by the last bullet point, I prefer an explicit raise:

if foo is None:
    raise ValueError("foo may not be None")

I actually use schema validation to enforce this at the edge so the rest of my code can make reasonable assumptions, and I'm explicit about whether each field may or may not be None.

My point is that if your variable can be None then you need the same pattern for the length check.

So for the Pythonic version:

if (foo is not None) and not foo:
   ...

For the explicit length check:

if (foo is not None) and (len(foo) == 0):
  ...

Honestly you're probably better off using type hints and catching such things with static checks and not adding the None check.