Installation | Topics | Beyond Lino
The Python Path¶
A collection of things to know when setting up the
PYTHONPATH or diagnosing related problems.
What is the Python Path?¶
- PYTHONPATH¶
It is an environment variable used by Python itself. It defines the places from where to import Python modules. See PYTHONPATH
Here is how to see your PYTHONPATH:
$ python -c 'import sys; print sys.path'
The mypy directory¶
Ac ommon practice is to create directory
~/mypy
(or C:\mypy under Windows)
where you hold your local Python projects.
You may choose some other location, but it should be
a name without spaces and non-ascii characters.
Then you add this directory to your Python Path by saying in your .bashrc (or whatever login script you use):
export PYTHONPATH = /home/mypy
(Under Windows you click around to find the place
where you can define environment variables and define
an environment variable PYTHONPATH with the value C:\\mypy).
The result is that any Python script in or below this directory is now available as an importable Python module.
For example
if you create a file ~/mypy/foo.py with the following content…
def hello():
print "Hello, world!"
… then you can import a module foo from any Python process,
independently of the current directory:
$ python
Python 2.7.1 (r271:86832, Nov 27 2010, 18:30:46) ...
Type "help", "copyright", "credits" or "license" for more information.
>\ >> import foo
>\ >> foo.hello()
Hello, world!
>\ >> from foo import hello
>\ >> hello()
Hello, world!
>\ >>
The local.pth file¶
In your mypy directory, create a file local.pth,
a plain txt file that contains a list of directories
which Python should also add to its path.
Under Debian, this file should look like this:
~/snapshots/lino
~/snapshots/django-dev
~/snapshots/appy
Under Windows it should have the following content:
c:\snapshots\lino
c:\snapshots\python-dateutil
c:\snapshots\appy
c:\snapshots\Cheetah-2.4.4
c:\snapshots\PyYAML-3.10\lib
Set the system-wide Python Path¶
The following approach can be useful if you want to provide system users with a development version of Django or some other Python package. It requires you to have root permission.
To modify the system-wide Python Path,
add the file local.pth to a directory that’s already on
your Python Path:
OS |
Recommended directory |
|---|---|
Debian Lenny |
|
Debian Squeeze |
|
Debian Wheezy |
|