[Tutor] Importing files not located on the home directory or standardard library
steve at pearwood.info
Fri Jun 18 16:48:59 CEST 2010
On Thu, 17 Jun 2010 05:10:32 pm Independent Learner wrote:
> Lets say I want to load a file called quiz located in C:\Users\Julius
> Hernandez\Desktop\Python2.6.5\Online Course\Chp.4
> How would I configure PYTHONPATH or .pth or what ever to import this
> file from IDLE
I don't use Windows, so I can't tell you the specific Windows commands
to use, but I'll tell you the general steps and you can convert them to
You need to:
(1) Create an environment variable called PYTHONPATH;
(2) Set it to the path (or paths) you want;
(3) Ensure it gets automatically re-created each time you log in.
(4) When you restart Python, it will add the value of PYTHONPATH to your
module search path.
Here is an example from Linux. I have this command in my .bashrc file:
The "export" shell command creates the environment variable PYTHONPATH
and sets it to "/home/steve/python/". By placing it in .bashrc, it will
automatically be executed each time I log in or start a new shell.
Alternatively, you can use a .pth file. That's probably better if you
have lots of directories to add. I've never done this, so take this
with a grain of salt:
(1) Find the location of your Python 2.6 installation. This is probably
something like C:\Applications\Python2.6.5\ or similar.
(2) Inside that directory should be another directory
called "site-packages". It may or may not already have files or folders
(3) Find, or create, a file called ".pth" inside site-packages. You may
need to instruct Windows to show hidden files.
(4) Add the line:
C:\Users\Julius Hernandez\Desktop\Python2.6.5\Online Course\Chp.4\
to that file, optionally together with
C:\Users\Julius Hernandez\Desktop\Python2.6.5\Online Course\Chp.1\
C:\Users\Julius Hernandez\Desktop\Python2.6.5\Online Course\Chp.2\
C:\Users\Julius Hernandez\Desktop\Python2.6.5\Online Course\Chp.3\
(5) Save and close the file, then restart Python.
> I am also having slight trouble understanding module packages as
> well, though I suspect it has something to do with not knowing how to
> configure PYTHONPATH or .pth files
A *module* is a single file containing Python code. Source code is
name.py (also name.pyw on Windows only) while compiled byte code is
name.pyc or name.pyo. There may be a few other extensions allowed on
some other platforms.
A *package* is a directory containing multiple modules which make up a
unified whole. Not every directory containing modules is a package --
you need a special file called __init__.py for Python to treat it as a
package. (That's underscore underscore i n i t underscore underscore
dot p y.)
If you have a directory structure like this:
then you have a package alpha containing two modules beta and gamma and
one sub-package delta. Now put the whole thing (the alpha directory
plus it's contents) somewhere in the Python path, and it will be
visible to Python. Then you can do this:
and then this:
x = alpha.delta.epsilon.some_function(1)
y = alpha.gamma.something(2)
z = alpha.something_else(3)
and so forth.
By the way, __init__.py doesn't have to contain anything, although it
can contain code. It just needs to exist.
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