Importing in Python

问题:

In Python 2.5, I import modules by changing environment variables. It works, but using site-packages does not. Is there another way to import modules in directories other than C:\Python25 ?

回答1:

On way is with PYTHONPATH environment variable. Other one is to add path to sys.path either directly by sys.path.append(path) or by defining .pth files and add them to with site.addsitedir(dirWithPths). Path files (.pth) are simple text files with a path in each line. Every .pth file in dirWithPths will be read.

回答2:

Directories added to the PYTHONPATH environment variable are searched after site-packages, so if you have a module in site-packages with the same name as the module you want from your PYTHONPATH, the site-packages version will win. Also, you may need to restart your interpreter and the shell that launched it for the change to the environment variable to take effect.

If you want to add a directory to the search path at run time, without restarting your program, add the directory to sys.path. For example:

import sys
sys.path.append(newpath)

If you want your new directory to be searched before site-packages, put the directory at the front of the list, like this:

import sys
sys.path.insert(0, newpath)

回答3:

Append the location to the module to sys.path.

Edit: (to counter the post below ;-) ) os.path does something completely different. You need to use sys.path.

sys.path.append("/home/me/local/modules")

回答4:

sys.path is a list to which you can append custom paths to search like this:

sys.path.append("/home/foo")