.pth files

**Adriano Varoli Piazza** · Aug 9 '05, 09:45 AM

Re: .pth files

Sylvain Thenault ha scritto:[color=blue]
> Hi there !
>
> I've some questions regarding pth files (which btw are undocumented in the
> python reference, is this intentional ?)
>
> I thought that I could use a .pth file to be able to import zope products
> from both INSTANCE_HOME/Products and ZOPE_HOME/lib/python/Products from
> outside zope:
>
>
> syt@musca:~$ cat cvs_work/Products.pth
> /home/syt/local/Zope-2.8.1-b1/Products
> /home/syt/local/Zope-2.8.1-b1/lib/python/Products
> syt@musca:~$
> syt@musca:~$ python
> Python 2.3.5 (#2, Jun 19 2005, 13:28:00)
> [GCC 3.3.6 (Debian 1:3.3.6-6)] on linux2
> Type "help", "copyright" , "credits" or "license" for more information.
>[color=green][color=darkred]
>>>>import sys
>>>>print sys.path[/color][/color]
>
> ['', '/home/syt/cvs_work', '/home/syt/cvs_work/prive/soft',
> '/home/syt/local/lib/python2.3/site-packages',
> '/home/syt/local/lib/python', '/usr/lib/python23.zip',
> '/usr/lib/python2.3', '/usr/lib/python2.3/plat-linux2',
> '/usr/lib/python2.3/lib-tk', '/usr/lib/python2.3/lib-dynload',
> '/usr/local/lib/python2.3/site-packages',
> '/usr/lib/python2.3/site-packages',
> '/usr/lib/python2.3/site-packages/Numeric',
> '/usr/lib/python2.3/site-packages/PIL',
> '/usr/lib/python2.3/site-packages/gtk-2.0',
> '/usr/lib/python2.3/site-packages/vtk_python', '/usr/lib/site-python']
>
> But as you can see,
> 1. the Products.pth file isn't considered at all, while for example
> PIL.pht in the site-packages is correctly detected
> 2. I'm not even sure that I can put several paths in a .pth file
>
> Is there a restriction on .pth location ? Is it possible to have multiple
> path in a pth file ?
>[/color]

From Learning Python, 2nd Ed:
"a relatively new feature of Python allows users to add valid
directories to the module search path by simply listing them, one per
line, in a text file whose name ends in a .pth suffix.

See also the docs for the site module in the Python Library reference.

--
Adriano Varoli Piazza
The Inside Out: http://moranar.com.ar
MSN: adrianomd@hotma il.com
ICQ: 4410132

**Sylvain Thenault** · Aug 9 '05, 09:55 AM

Re: .pth files

On Tue, 09 Aug 2005 09:37:47 +0000, Adriano Varoli Piazza wrote:
[color=blue]
> Sylvain Thenault ha scritto:[color=green]
>> Hi there !
>>
>> I've some questions regarding pth files (which btw are undocumented in
>> the python reference, is this intentional ?)
>>
>> I thought that I could use a .pth file to be able to import zope
>> products from both INSTANCE_HOME/Products and
>> ZOPE_HOME/lib/python/Products from outside zope:
>>
>>
>> syt@musca:~$ cat cvs_work/Products.pth
>> /home/syt/local/Zope-2.8.1-b1/Products
>> /home/syt/local/Zope-2.8.1-b1/lib/python/Products syt@musca:~$
>> syt@musca:~$ python
>> Python 2.3.5 (#2, Jun 19 2005, 13:28:00) [GCC 3.3.6 (Debian 1:3.3.6-6)]
>> on linux2 Type "help", "copyright" , "credits" or "license" for more
>> information.
>>[color=darkred]
>>>>>import sys
>>>>>print sys.path[/color]
>>
>> ['', '/home/syt/cvs_work', '/home/syt/cvs_work/prive/soft',
>> '/home/syt/local/lib/python2.3/site-packages',
>> '/home/syt/local/lib/python', '/usr/lib/python23.zip',
>> '/usr/lib/python2.3', '/usr/lib/python2.3/plat-linux2',
>> '/usr/lib/python2.3/lib-tk', '/usr/lib/python2.3/lib-dynload',
>> '/usr/local/lib/python2.3/site-packages',
>> '/usr/lib/python2.3/site-packages',
>> '/usr/lib/python2.3/site-packages/Numeric',
>> '/usr/lib/python2.3/site-packages/PIL',
>> '/usr/lib/python2.3/site-packages/gtk-2.0',
>> '/usr/lib/python2.3/site-packages/vtk_python', '/usr/lib/site-python']
>>
>> But as you can see,
>> 1. the Products.pth file isn't considered at all, while for example
>> PIL.pht in the site-packages is correctly detected
>> 2. I'm not even sure that I can put several paths in a .pth file
>>
>> Is there a restriction on .pth location ? Is it possible to have
>> multiple path in a pth file ?
>>
>>[/color]
> From Learning Python, 2nd Ed:
> "a relatively new feature of Python allows users to add valid directories
> to the module search path by simply listing them, one per line, in a text
> file whose name ends in a .pth suffix.
>
> See also the docs for the site module in the Python Library reference.[/color]

ha, so that's where it's documented !
so answer are:
1. Products.pth are only considered in standard site-packages and
site-python directories
2. yes, it's possible

Now, the question become: why can't we use pth files in other path
specified by the PYTHONPATH environement variable ?

--
Sylvain Thénault LOGILAB, Paris (France).

http://www.logilab.com http://www.logilab.fr http://www.logilab.org

**Richie Hindle** · Aug 9 '05, 10:05 AM

Re: .pth files

[Sylvain][color=blue]
> I've some questions regarding pth files (which btw are undocumented in the
> python reference, is this intentional ?)[/color]

site:docs.python.org pth - Google Suche

http://google.com/search?q=site:docs.python.org%20pth

The first hit explains how .pth files work (although it's the sort of
documentation that makes Xah Lee explode with fury).

--
Richie Hindle
richie@entrian. com

**Erik Max Francis** · Aug 9 '05, 10:05 AM

Re: .pth files

Richie Hindle wrote:
[color=blue]
> http://google.com/search?q=site:docs.python.org%20pth
>
> The first hit explains how .pth files work (although it's the sort of
> documentation that makes Xah Lee explode with fury).[/color]

That just makes it all the more delicious.

--
Erik Max Francis && max@alcyone.com && http://www.alcyone.com/max/
San Jose, CA, USA && 37 20 N 121 53 W && AIM erikmaxfrancis
There is another world, which is not of men.
-- Li Bai

**Neil Benn** · Aug 9 '05, 11:15 AM

Re: .pth files

Sylvain Thenault wrote:
[color=blue]
>On Tue, 09 Aug 2005 09:37:47 +0000, Adriano Varoli Piazza wrote:
>
>
>[color=green]
>>Sylvain Thenault ha scritto:
>>
>>[color=darkred]
>>>Hi there !
>>>
>>>I've some questions regarding pth files (which btw are undocumented in
>>>the python reference, is this intentional ?)
>>>
>>>I thought that I could use a .pth file to be able to import zope
>>>products from both INSTANCE_HOME/Products and
>>>ZOPE_HOME/lib/python/Products from outside zope:
>>>
>>>
>>>syt@musca: ~$ cat cvs_work/Products.pth
>>>/home/syt/local/Zope-2.8.1-b1/Products
>>>/home/syt/local/Zope-2.8.1-b1/lib/python/Products syt@musca:~$
>>>syt@musca: ~$ python
>>>Python 2.3.5 (#2, Jun 19 2005, 13:28:00) [GCC 3.3.6 (Debian 1:3.3.6-6)]
>>>on linux2 Type "help", "copyright" , "credits" or "license" for more
>>>informatio n.
>>>
>>>
>>>
>>>>>>import sys
>>>>>>print sys.path
>>>>>>
>>>>>>
>>>['', '/home/syt/cvs_work', '/home/syt/cvs_work/prive/soft',
>>> '/home/syt/local/lib/python2.3/site-packages',
>>> '/home/syt/local/lib/python', '/usr/lib/python23.zip',
>>> '/usr/lib/python2.3', '/usr/lib/python2.3/plat-linux2',
>>> '/usr/lib/python2.3/lib-tk', '/usr/lib/python2.3/lib-dynload',
>>> '/usr/local/lib/python2.3/site-packages',
>>> '/usr/lib/python2.3/site-packages',
>>> '/usr/lib/python2.3/site-packages/Numeric',
>>> '/usr/lib/python2.3/site-packages/PIL',
>>> '/usr/lib/python2.3/site-packages/gtk-2.0',
>>> '/usr/lib/python2.3/site-packages/vtk_python', '/usr/lib/site-python']
>>>
>>>But as you can see,
>>>1. the Products.pth file isn't considered at all, while for example
>>> PIL.pht in the site-packages is correctly detected
>>>2. I'm not even sure that I can put several paths in a .pth file
>>>
>>>Is there a restriction on .pth location ? Is it possible to have
>>>multiple path in a pth file ?
>>>
>>>
>>>
>>>[/color]
>> From Learning Python, 2nd Ed:
>>"a relatively new feature of Python allows users to add valid directories
>>to the module search path by simply listing them, one per line, in a text
>>file whose name ends in a .pth suffix.
>>
>>See also the docs for the site module in the Python Library reference.
>>
>>[/color]
>
>ha, so that's where it's documented !
>so answer are:
>1. Products.pth are only considered in standard site-packages and
> site-python directories
>2. yes, it's possible
>
>Now, the question become: why can't we use pth files in other path
>specified by the PYTHONPATH environement variable ?
>
>
>[/color]
Hello,

I've been doing some work on that recently, if your do want to
include .pth files specified by a different location then you have to do
some work, here are a couple of solutions:

* Site.py is prompted to load a sitecustomise.p y file which is
located in the Lib directory - if it is there. This file is
automatically executed on the start up of python. Here you can
look for a command line argument (or a local config file) passed
in - you can then go and find the .pth file yourself. The code to
pull in .pth stuff is located in the site.py file - you can import
this function and use it but I don't do that for two reasons
(instead I pull across my own copy - effectivly freezing that
implementation) :

1. You are creating a circular reference
2. I can find no docs or imformation about using the functions
in the site.py file so therefore I have to assume that the
functions in the site.py file are not designed to be used
this way and therefore shouldn't be relied upon to be stable
or even present across python releases (I'm a conservative
programmer.

This however can be problematic if you are managing a large
number of client installs as you will need to have a local file on the
local box - thereby making upgrading the clients installs difficult.

* I created a python module which can receive command line arguments
setting up site-package directories and pythonpath which executes
as a file, this also receives an argument of which python file to
execute after this. This means that the file which does this work
can be located anywhere (ie on your company server) - making
release management easier. However this solution requires more work.
* You could copy the java method using zip files with a manifest in
the same way Java uses jar files - I say could because I havn't
done this but it is the way I distribute Java apps - nice and
clean, also installed my own JRE with my program - that way I have
complete control (anyone that complains about using hard drive
space can go back to using their ZX81 :-)) over my environment.

If you are not worried about managing the release stuff and
sitecustomise works fine for you then this is the way to go as it is the
simplest (less code means more reliable). However be aware that the
sitepackage directory on the python install will automatically be
included and you could have two versions of the same package in
sys.path. Finally, one last thing - beware if you are on windows as
some path information is written in the registry and this is included
automatically.

Cheers,

Neil

--

Neil Benn
Senior Automation Engineer
Cenix BioScience
BioInnovations Zentrum
Tatzberg 47
D-01307
Dresden
Germany

Tel : +49 (0)351 4173 154
e-mail : benn@cenix-bioscience.com
Cenix Website : http://www.cenix-bioscience.com

**Peter Hansen** · Aug 9 '05, 12:05 PM

Re: .pth files

Neil Benn wrote:[color=blue]
> * Site.py is prompted to load a sitecustomise.p y file which is
> located in the Lib directory - if it is there. This file is
> automatically executed on the start up of python. Here you can
> look for a command line argument (or a local config file) passed
> in - you can then go and find the .pth file yourself. The code to
> pull in .pth stuff is located in the site.py file - you can import
> this function and use it but I don't do that for two reasons
> (instead I pull across my own copy - effectivly freezing that
> implementation) :
>
> 1. You are creating a circular reference[/color]

The "import sitecustomize" stuff is placed effectively at the end of
site.py, so it should be quite safe to "import site" from your
sitecustomize.p y file and use the functions there.
[color=blue]
> 2. I can find no docs or imformation about using the functions
> in the site.py file so therefore I have to assume that the
> functions in the site.py file are not designed to be used
> this way and therefore shouldn't be relied upon to be stable
> or even present across python releases (I'm a conservative
> programmer.[/color]

While I can't fault your caution, we've been using a few things in
site.py from sitecustomize for a while with no problems (across releases
from Python 1.5.2 to Python 2.4). The functions are documented in the
site.py source itself, of course, at least in a cursory fashion, and
while there have been changes over versions, I don't recall anything
causing breakage. Normally I'd quite agree about staying away, but for
something like this (i.e. not a core part of an application, but
something to set up the environment instead) I'd say "go for it".

-Peter

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