OK, I'm impressed! I've written about and taught Python for almost 20 years. I never realized `in` was a chained comparison. I'm pretty sure I've never seen it used that way "in the wild." I also never tried using `is` in a chained way until just now. That said, there are at least three things perverse about the examples below, and they should *definitely* never be used in real code. This is vaguely plausible (for variable defined in some more interesting way where the substring relation is not so obvious; say content read from files):

...

...

a = "a" b = "abc" c = "abcde" a in b in c True

On Tue, Feb 28, 2017 at 6:56 PM, 语言破碎处 <mlet_it_bew@126.com> wrote:

I'm bited once: >>> '' in {} == False False >>> ('' in {}) == False True

# '' in {} == False ==>> ('' in {}) and ({} == False) ==>> False!

I think only compare operations should be chained.

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