Shall I worry about python2/3 compatibility when using library?

[Terry Reedy]

On 8/30/2018 10:27 PM, Stone Zhong wrote:
> Hi there,
> 
> I think the fact is:
> - There are still considerable amount of people still using python2
> - Python2 user will eventually upgrade to python3
> 
> So any library not written in a compatible way will either break now for python2 user, or will break in the future for python3 user. So I suppose all library developer are writing compatible code, is that a fair assumption?

No.  Many people write new libraries only for recent version of Python 
3.  Many people who have written Python 2 and 3 compatible libraries, or 
Python 2 and Python 3 versions of of their library, have or will drop 
Python 2 support for enhancements and even bugfixes for their library.

That said, some people will continue to use existing python 2 code for a 
decade or more.

-- 
Terry Jan Reedy