#!/usr/bin/python or #!/usr/bin/env python?

**Steven Bethard** · Aug 8 '06, 07:15 PM

Re: #!/usr/bin/python or #!/usr/bin/env python?

John Salerno wrote:

I understand the difference, but I'm just curious if anyone has any
strong feelings toward using one over the other? I was reading that a
disadvantage to the more general usage (i.e. env) is that it finds the
first python on the path, and that might not be the proper one to use.

I don't see how that's any different from when the Python at
/usr/bin/python isn't the right one to use. I know that's true at my
university:

$ /usr/bin/python -V
Python 2.2.3
$ /usr/local/python/bin/python -V
Python 2.4.3

With this setup, the one in /usr/bin is for the OS and is seldom
updated, and the one in /usr/local is for users and is updated frequently.

Sure, if someone doesn't put /usr/local/python/bin on their PATH,
they're not going to get the right Python, but I don't write code to
Python 2.2 anymore, so if I use ``#!/usr/bin/python`` my code will
probably just fail.

Obviously, in my own code, I only use ``#!/usr/bin/env python``.

STeVe

**Martin v. Löwis** · Aug 8 '06, 07:25 PM

Re: #!/usr/bin/python or #!/usr/bin/env python?

John Salerno schrieb:

I understand the difference, but I'm just curious if anyone has any
strong feelings toward using one over the other?

I use /usr/bin/env if I don't know what the operating system is;
some systems don't have Python in /usr/bin. I use /usr/bin/pythonX.Y
if I want a specific version on a specific operating system (typically
Linux). I use /usr/bin/python when I'm too lazy to think about it
thoroughly.

Regards,
Martin

**skip@pobox.com** · Aug 8 '06, 07:35 PM

Re: #!/usr/bin/python or #!/usr/bin/env python?

JohnI understand the difference, but I'm just curious if anyone has
Johnany strong feelings toward using one over the other?

#!/usr/bin/python -never

#!/usr/bin/env python -always

Strong enough?

JohnI was reading that a disadvantage to the more general usage
John(i.e. env) is that it finds the first python on the path

That's generally the one you want. On most systems /usr/bin/python will be
the system-provided one (e.g. the one that came with your Linux
distribution). You might prefer a Python of more recent vintage though.
That's commonly installed in /usr/local/bin/python and /usr/local/bin is
generally ahead of /usr/bin in PATH.

JohnAnd is Python found in directories other than /usr/bin often
Johnenough to justify using the more general form?

On my Mac I install most stuff in ~/local simply so I don't need to be
root and don't disturb the system-provided software. In cases where other
users need to run such tools I generally use /usr/local.

Skip

**John Salerno** · Aug 8 '06, 07:55 PM

Re: #!/usr/bin/python or #!/usr/bin/env python?

skip@pobox.com wrote:

On most systems /usr/bin/python will be
the system-provided one (e.g. the one that came with your Linux
distribution). You might prefer a Python of more recent vintage though.
That's commonly installed in /usr/local/bin/python and /usr/local/bin is
generally ahead of /usr/bin in PATH.

Ah, that answered my next question too! I guess I'll stick with the env
method, since I like the more general, abstract stuff over the absolute
anyway.

**Erik Max Francis** · Aug 8 '06, 08:15 PM

Re: #!/usr/bin/python or #!/usr/bin/env python?

John Salerno wrote:

I understand the difference, but I'm just curious if anyone has any
strong feelings toward using one over the other? I was reading that a
disadvantage to the more general usage (i.e. env) is that it finds the
first python on the path, and that might not be the proper one to use. I
don't know if that's a real issue most of the time, but it's at least
something to consider.
>
And is Python found in directories other than /usr/bin often enough to
justify using the more general form?

Yes. If Python (or indeed any other well-behaving software) is
installed manually, it will _not_ be installed in /usr/bin. /usr is
where your primary OS/distribution installation goes. Additional
software goes elsewhere, such as /usr/local.

Always prefer to use env over a hardcoded path, because that hardcoded
path will invariably be wrong. (Yes, for those about to nitpick, it's
conceivable that env might be somewhere other than /usr/bin. However,
that is very rare and results in a no-win situations regardless of the
issue of where Python is installed.)

--
Erik Max Francis && max@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
Never contend with a man who has nothing to lose.
-- Baltasar Gracian, 1647

**Erik Max Francis** · Aug 8 '06, 08:15 PM

Re: #!/usr/bin/python or #!/usr/bin/env python?

Martin v. Löwis wrote:

I use /usr/bin/env if I don't know what the operating system is;
some systems don't have Python in /usr/bin. I use /usr/bin/pythonX.Y
if I want a specific version on a specific operating system (typically
Linux).

Even there, /usr/bin/env pythonX.Y would be a better choice. (Maybe
that's what you meant.)

--
Erik Max Francis && max@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
Never contend with a man who has nothing to lose.
-- Baltasar Gracian, 1647

**Martin v. Löwis** · Aug 8 '06, 09:25 PM

Re: #!/usr/bin/python or #!/usr/bin/env python?

Erik Max Francis schrieb:

>I use /usr/bin/env if I don't know what the operating system is;
>some systems don't have Python in /usr/bin. I use /usr/bin/pythonX.Y
>if I want a specific version on a specific operating system (typically
>Linux).

>
Even there, /usr/bin/env pythonX.Y would be a better choice. (Maybe
that's what you meant.)

I'm uncertain. When I refer to /usr/bin/python2.3, I know I get the
system vendor's installation. When I use /usr/bin/env python2.3, I
may get something that somebody has build and which may not work
at all, or lack certain add-on packages that the script needs.
It's bad when the script works for some users but fails for others.

Regards,
Martin

**Stephan Kuhagen** · Aug 9 '06, 05:55 AM

Re: #!/usr/bin/python or #!/usr/bin/env python?

Always prefer to use env over a hardcoded path, because that hardcoded

path will invariably be wrong. (Yes, for those about to nitpick, it's
conceivable that env might be somewhere other than /usr/bin. However,
that is very rare and results in a no-win situations regardless of the
issue of where Python is installed.)

Don't yell at me for bringing in another language, but I really like the
trick, Tcl does:

#!/bin/sh
# The next line starts Tcl \
exec tclsh "$0" "$@"

This works by the somewhat weird feature of Tcl, that allows comments to be
continued in the next line with "\" at the end of the comment-line. It
looks unfamiliar, but has several advantages, I think. First it's really
VERY unlikely, that there is no /bin/sh (while I found systems with
different places for env), and you can add some other features at or before
the actual call of the interpreter, i.e. finding the right or preferred
version... - This way I coded a complete software-installer, that runs
either as a Tcl/Tk-Script with GUI, or as bash-script, when no Tcl is
available. - I really would like to have something like that for python,
but I did not find a way to achieve that, yet.

Regards
Stephan

**Micha³ Bartoszkiewicz** · Aug 9 '06, 06:55 AM

Re: #!/usr/bin/python or #!/usr/bin/env python?

On 2006-08-09 at 08:02:03 (+0200), Stephan Kuhagen wrote:

Don't yell at me for bringing in another language, but I really like the
trick, Tcl does:
>

#!/bin/sh
# The next line starts Tcl \
exec tclsh "$0" "$@"

>
This works by the somewhat weird feature of Tcl, that allows comments to be
continued in the next line with "\" at the end of the comment-line. It
looks unfamiliar, but has several advantages, I think. First it's really
VERY unlikely, that there is no /bin/sh (while I found systems with
different places for env), and you can add some other features at or before
the actual call of the interpreter, i.e. finding the right or preferred
version... - This way I coded a complete software-installer, that runs
either as a Tcl/Tk-Script with GUI, or as bash-script, when no Tcl is
available. - I really would like to have something like that for python,
but I did not find a way to achieve that, yet.

You could use:
#!/bin/sh
"""exec" python "$0" "$@"""
:)

--
__ _______________ _______________ _______________ _______________ ________
| \/ | Micha³ Bartoszkiewicz <embe@magma-net.pl | _ )
| |\/| | GG:2298240 | _ \
|_| |_|_For all resources, whatever it is, you need more. [RFC1925]_|___/

**Stephan Kuhagen** · Aug 9 '06, 07:15 AM

Re: #!/usr/bin/python or #!/usr/bin/env python?

MichaÅ‚ Bartoszkiewicz wrote:

#!/bin/sh
"""exec" python "$0" "$@"""

Wow, cool... I like that!

Stephan

**Erik Max Francis** · Aug 9 '06, 07:15 AM

Re: #!/usr/bin/python or #!/usr/bin/env python?

Stephan Kuhagen wrote:

MichaÅ‚ Bartoszkiewicz wrote:
>

>#!/bin/sh
>"""exec" python "$0" "$@"""

>
Wow, cool... I like that!

Only someone genuinely fond of the Tcl hack could ...

--
Erik Max Francis && max@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
No man who needs a monument ever ought to have one.
-- Nathaniel Hawthorne

**Stephan Kuhagen** · Aug 9 '06, 07:35 AM

Re: #!/usr/bin/python or #!/usr/bin/env python?

Erik Max Francis wrote:

>>#!/bin/sh
>>"""exec" python "$0" "$@"""

>>
>Wow, cool... I like that!

>
Only someone genuinely fond of the Tcl hack could ...

True, I admit, I'm a Tcl-Addict... But I really love Python too for many
reasons. But I miss features and tricks in both languages that I have in
the other...

Interleaving the script-language with shell-scripting was one of them. So
I'm a little bit happier with Python now... ;-)

Stephan

**ZeD** · Aug 9 '06, 07:45 AM

Re: #!/usr/bin/python or #!/usr/bin/env python?

Stephan Kuhagen wrote:

>#!/bin/sh
>"""exec" python "$0" "$@"""

>
Wow, cool... I like that!

yeah, but...

$ cat test.py
#!/bin/sh
"""exec" python "$0" "$@"""

print "Hello, world"
$ file test.py
test.py: Bourne shell script text executable

--
Under construction

**Stephan Kuhagen** · Aug 9 '06, 08:05 AM

Re: #!/usr/bin/python or #!/usr/bin/env python?

ZeD wrote:

print "Hello, world"
$ file test.py
test.py: Bourne shell script text executable

Yes, the same happens with all Tcl-Scripts. I like to see this as a bug in
"file", not in the scripting...

Stephan

#!/usr/bin/python or #!/usr/bin/env python?

#!/usr/bin/python or #!/usr/bin/env python?

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment

Comment