[rtpg]

Python code rarely looks like this

For things like optional arguments you usually use None with an "if l is None" parameter

Meanwhile you can't iterate over None, so [x for x in None] blows up

Closure (to my understanding) allows a null value in the place of any empty seq. This seems like a major bug swallower to me

[yen223]

> Python code rarely looks like this

Using implicit truthiness to test for empty sequences is idiomatic Python, for better or worse.

[rtpg]

Sorry, you're actually very right. I think I misread this in the case of a default argument example (which at least for codebases I work with are diligent about doing None tests for ) but if you know that the value is set to a sequence then the boolean test is common