Importing In Python

Is it possible to import modules based on location?

(eg. do all modules i import have to be in /usr/lib64/python2.5/ or a similar dir?)

I'd like to import a module that's local to the current script.

From stackoverflow

• You can edit your PYTHONPATH to add or remove locations that python will search whenever you attempt an import.

• • python will import from the current directory by default.

  • sys.path is the variable that controls where python searches for imports.

• You can extend the path at runtime like this:

  sys.path.extend(map(os.path.abspath, ['other1/', 'other2/', 'yourlib/']))
  

• You can import module that are in the same path the module you are importing to. For example:

  Directory contains: mod1.py, mod2.py

  mod2.py
  --------
  import mod1
  

  Or you can add any directory to your PYTHON_PATH variable:

  import sys
  sys.path.extend('/user/some/other/directory')
  import mod1
  

• It searches in ./lib by default.

• For low-level control over the import process, the imp module lets you import modules from arbitrary open files under arbitrary names.

  For example, if this is foo.py:

  def x():
      print 'hello, world'
  

  Then this code:

  import imp
  
  with open('foo.py', 'r') as module_file:
      imp.load_module('module_name', module_file, '', ('', 'r', imp.PY_SOURCE))
  
  import module_name
  
  module_name.x()
  

  prints "hello, world".

• Use init.py

  The only problem with doing dynamic modification of sys.path is that you need to repeat it in every script and hard-code the pathnames. That gets messy and non DRY if you have even two or three files.

  Instead, if your file structure looks like this:

  ~/foo/__init__.py
  ~/foo/foo.py
  ~/foo/bar/__init__.py
  ~/foo/bar/baz.py
  

  Here the init.py's are blank files created with touch, while foo.py and baz.py are actual python scripts. Then you can do something like this:

  import sys
  try:
      from foo import foo
      from foo.bar import baz
  except ImportError:
      "%s is not in %s. Add to your PYTHONPATH in ~/.bashrc" % \
      (os.path.expanduser("~/foo"),sys.path)
  

  Structuring your stuff as a package from the beginning is a little more work but makes it much easier to scale the project later and to see where imports are coming from. Moreover, if you move stuff around, you can use a single symlink rather than doing a find/replace through your codebase. E.g. if you moved '~/foo' to '~/downloads/foo', just do this:

  cd ~
  ln -s ~/downloads/foo foo
  

  And all your imports will still work.