Re: python3 script header and rhel8

[John Snow]

On 1/28/20 11:07 AM, Daniel P. Berrangé wrote:
> On Tue, Jan 28, 2020 at 03:44:04PM +0000, Vladimir Sementsov-Ogievskiy wrote:
>> Hi all!
>>
>> Hmm Qemu dropped support for python2, and anyway python2 is not supported 
>> now at all.
>>
>> Still, we have a lot of "#!/usr/bin/env python" headings in our scripts, 
>> which is
>> unsupported by rhel8 by default. So, for example, because of such line in
>> tests/qemu-iotests/nbd-fault-injector.py, iotest 277 fails.
>>
>> Of course, it's simple to set python in rhel8 to be python3... But should we 
>> fix
>> all the headings to be "#!/usr/bin/env python3"? Or what is the correct 
>> heading
>> for scripts in a new python3 world?
> 
> Using "#!/usr/bin/env python3" is probably our best choice, as it
> makes it absolutely clear we're not happy with a python2 impl.
> 

On using 'env' or not: for any script anticipated to be executed
directly from the command line, a hardcoded path will inhibit idiomatic
virtual environment usage, so 'env' is preferred.

On python vs python2 vs python3:

https://www.python.org/dev/peps/pep-0394/

PEP 0394 states that 'python3' should be available and that 'python' is
optional.

That answers that, in my opinion. Let's make `#!/usr/bin/env python3`
ubiquitous.

--js