Interesting that more people weren't asking for more explanation on this. I feel like the article did a poor job but other commenters explained it well. More co

Interesting that more people weren't asking for more explanation on this. I feel like the article did a poor job but other commenters explained it well. More commonly I see this with `def f(x=list()):...` or similar. Linters will even warn about it. It really shows a lack of Python knowledge, so I'll jump on the bandwagon of rewriting this with such pressure was a bad idea.