问题
What exactly is the <> operator in Python, and why is it undocumented (as far as I can tell)?
Is it the same as != or is not?
回答1:
In Python 2.x, <> is the same as != (i.e. "not equal to", rather than is not which is "not identical to"), but the latter is preferred:
The comparison operators
<>and!=are alternate spellings of the same operator.!=is the preferred spelling;<>is obsolescent.
In 3.x, <> has been removed and only != exists.
回答2:
It is documented, but you're not supposed to use it. Your guess about it being equivalent to != is correct. Quoting the Python 2 documentation:
!=can also be written<>, but this is an obsolete usage kept for backwards compatibility only. New code should always use!=.
Then as part of the general cleanup of Python 3, the operator was removed entirely:
Removed
<>(use!=instead).
Historical note
It goes back quite a long way; at least as far as Python 1.4. I found an entry in the old docs:
<>and!=are alternate spellings for the same operator. (I couldn't choose between ABC and C! :-)
The docs started recommending != with Python 1.5.2p2.
来源：https://stackoverflow.com/questions/29238871/what-is-the-python-operator