Hi Nick, On Mon, Aug 30, 2021 at 4:25 PM Nick Parlante <nick@cs.stanford.edu> wrote:
I don't know Chris, doesn't this just show that If you construct a class with a, shall we say, "oddball" definition of ==, then using == on that class gets oddball results. And it goes without saying that we all understand that None and False and True (the dominant cases where PEP8 is forcing "is") will always have sensible definitions of ==.
If you have `if x == None:`, you don't only have to care about whether `None` has an "oddball" definition of ==, you also have to care about whether the type of `x` does! Since in many of these cases `x` is something passed in from outside the function, you may not have any idea about or control over its type. That's why people are telling you that almost all the occurrences you've found would in fact be unsafe if changed from `is` to `==`, and it's very rare that you can "eyeball" a particular case and declare confidently that it would be fine to switch it from `is` to `==`. Carl