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

[Glenn Linderman]

On 3/8/2011 12:02 PM, Terry Reedy wrote:
> On 3/7/2011 9:31 PM, Reliable Domains wrote:
>
>> The launcher need not be called "python.exe", and maybe it would be
>> better called #@launcher.exe (or similar, depending on its exact
>> function details).
>
> I do not know that the '#@' part is about, but pygo would be short and 
> expressive.
>

If my proposal to make a line starting with #@ to be used instead of the 
Unix #! (#@ could be on the first or second line, to allow 
cross-platform scripts to use both, and Windows only scripts to not have 
#!), then #@launcher.exe (and #@launcherw.exe I suppose) would reflect 
the functionality of the launcher, which need not be tightly tied to 
Python, if it uses a separate line.  But the launcher should probably 
not be the thing invoked from the command line, only implicitly when 
running scripts by naming them as the first thing on the command line.

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"

Now that I've had this idea, one might want to create other "2nd 
character" codes after the Unix #! line... one could have

#! Unix command processor
#@ Windows command processor
#$ OS/2 command processor
#% Alternate Windows command processor.

One could even port it to Unix:

#!/usr/bin/#@launcher
#@c:\python2.6\python.exe
#^/usr/bin/python2.5
#&/usr/bin/mono/IronPython2.6 for .NET 4.0/ipy.exe
#  I made up the line above, having no knowledge of Mono, but I think 
you get the idea

Choice of command line would be an environment variable, I suppose, that 
the launcher would look at, or if none, then a system-specific default.  
It would have to search forward in the file until it finds the 
appropriate prefix or a line not starting with #, or starting with "# " 
or "##", at which point it would give up.

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