.pth files

[Sylvain Thenault]

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.['', '/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 ?

 

[Adriano Varoli Piazza]

Sylvain Thenault ha scritto:

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.

['', '/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 ?

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.

 

[Sylvain Thenault]

Sylvain Thenault ha scritto:

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.

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 ?

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.

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 ?

 

[Richie Hindle]

[Sylvain]

I've some questions regarding pth files (which btw are undocumented in the
python reference, is this intentional ?)

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

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

 

[Erik Max Francis]

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

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

That just makes it all the more delicious.

 

[Neil Benn]

Sylvain Thenault ha scritto:

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.



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 ?

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.

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 ?

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.py 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 : (e-mail address removed)
Cenix Website : http://www.cenix-bioscience.com

 

[Peter Hansen]

* Site.py is prompted to load a sitecustomise.py 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

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.py file and use the functions there.

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.

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