[Python-Dev] [PEPs] Support the /usr/bin/python2 symlink upstream

[Mark Hammond]

On 9/03/2011 1:43 PM, Glenn Linderman wrote:
> I'm of the opinion that attempting to parse a Unix #! line, and intuit
> what would be the equivalent on Windows is unnecessarily complex and
> error prone, and assumes that the variant systems are configured using
> the same guidelines (which the Python community may espouse, but may not
> be followed by all distributions, sysadmins, or users). That's why I
> propose a different line for Windows... it is as simple as the
> long-proven Unix #! line, but imposes no restrictions on or requirements
> that there be a #! line; it has more flexibility in that it could invoke
> different versions or provide different options on Unix and Windows if
> necessary for some environments.
>
> #!/usr/bin/env python2.6 -B
> #@c:\python26\python2.6.exe
>
> or
>
> #!/usr/bin/python2.5
> #@"C:\Program Files (x86)\IronPython 2.6 for .NET 4.0\ipy.exe"

I don't think that buys us much.  A script with "#!/usr/bin/env python" 
could be distributed with an expectation it will work across various 
different machines (and possibly even different operating systems).  A 
script with "c:\..." could not be distributed and expected to work 
reliably anywhere.  ie, any script with a #! line (or even a #@ line) 
with a fully qualified Windows path can only be expected to work on a 
single machine - so there is no need to support both #! and #@ as the 
script is not even cross-machine portable, let alone cross-platform 
portable.

The only way to expect a #! line to work across machines would be to 
have a "virtual" path - eg just "python2.6" without any path specifier 
at all.  In that case, I see no problem with reusing the #! from *nix 
systems and treating "/usr/bin" etc as a "virtual" specifier on Windows. 
  If people find a need on Windows to add a fully-qualified path to this 
line (whatever the spelling), they are implicitly saying this script 
works only on the current machine.

IOW, as soon as someone has:

#!/usr/bin/env python2.6 -B
#@c:\python26\python2.6.exe

in their script, the script is targeted at exactly 1 specific machine, 
so why not just reuse the #! syntax?  OTOH, if an existing script has:

#!/usr/bin/env python2.6 -B

They are attempting to declare in a portable way that Python 2.6 is 
necessary - so why force them to add a #@ line to make it work on 
Windows when the #! line is the only clue Windows needs to make it work 
automagically?

Cheers,

Mark