On 17/10/2011 9:10 PM, Sam Partington wrote:
Hello all,
I was surprised to see that the excellent pylauncher doesn't do the
magic shebang processing if you give it any python command line
options. e.g. Given
#!/usr/bin/env python2.6
import sys
print(sys.executable)
C:\>py test.py
C:\Python26\python.exe
C:\>py -utt test.py
C:\Python27\python.exe
It is spelled out that it shouldn't do so in the pep :
"Only the first command-line argument will be checked for a shebang line
and only if that argument does not start with a '-'."
But I can't really see why that should be the case. What is the
rational behind this?
It really is a combination of 2 things:
* The key use-case for the launcher is to be executed implicitly - ie,
the user types just "foo.py". In that scenario there is no opportunity
for the user to specify any args between the name of the executable and
of the script. IOW, the expectation is that people will not type "py
foo.py", but instead just type "foo.py".
* A desire to avoid command-line parsing in the launcher or to make some
options "more equal" then others. Eg, you mention later that -c and -m
should be special, but what about -w or -Q? What about new options in
future versions?
It is very surprising to the user that adding a
simple option like -tt should change the way the launcher behaves.
The PEP also states that the launcher should show the python help if
'-h' is specified :
"If the only command-line argument is "-h" or "--help", the launcher will
print a small banner and command-line usage, then pass the argument to
the default Python. This will cause help for the launcher being printed
followed by help for Python itself. The output from the launcher will
clearly indicate the extended help information is coming from the
launcher and not Python."
To me that would suggest to end users that they can use any of the
command line options with the launcher, and they should behave as if
you had called python directly.
I think the language is fairly clear - only the help options are special
and no other options will work.
...
Incidentally whilst implementing this I also noticed a bug in the
pylauncher whereby the py launcher would incorrectly treat "py t3" as
a request for python version as if '-3' had been specified. I have a
small patch that fixes this and implements the above for pylauncher
with extra tests if there is interest.
That certainly sounds like a bug and a patch sent to
https://bitbucket.org/vinay.sajip/pylauncher will be appreciated!
PS I have been lurking for a while, hello everyone.
Hi and cheers! :)
Mark
_______________________________________________
Python-Dev mailing list
Python-Dev@python.org
http://mail.python.org/mailman/listinfo/python-dev
Unsubscribe:
http://mail.python.org/mailman/options/python-dev/archive%40mail-archive.com
