Lib/lib-old/addpack.py

   1 # This module provides standard support for "packages".
   2 #
   3 # The idea is that large groups of related modules can be placed in
   4 # their own subdirectory, which can be added to the Python search path
   5 # in a relatively easy way.
   6 #
   7 # The current version takes a package name and searches the Python
   8 # search path for a directory by that name, and if found adds it to
   9 # the module search path (sys.path).  It maintains a list of packages
  10 # that have already been added so adding the same package many times
  11 # is OK.
  12 #
  13 # It is intended to be used in a fairly stylized manner: each module
  14 # that wants to use a particular package, say 'Foo', is supposed to
  15 # contain the following code:
  16 #
  17 #   from addpack import addpack
  18 #   addpack('Foo')
  19 #   <import modules from package Foo>
  20 #
  21 # Additional arguments, when present, provide additional places where
  22 # to look for the package before trying sys.path (these may be either
  23 # strings or lists/tuples of strings).  Also, if the package name is a
  24 # full pathname, first the last component is tried in the usual way,
  25 # then the full pathname is tried last.  If the package name is a
  26 # *relative* pathname (UNIX: contains a slash but doesn't start with
  27 # one), then nothing special is done.  The packages "/foo/bar/bletch"
  28 # and "bletch" are considered the same, but unrelated to "bar/bletch".
  29 #
  30 # If the algorithm finds more than one suitable subdirectory, all are
  31 # added to the search path -- this makes it possible to override part
  32 # of a package.  The same path will not be added more than once.
  33 #
  34 # If no directory is found, ImportError is raised.
  35
  36 _packs = {}                             # {pack: [pathname, ...], ...}
  37
  38 def addpack(pack, *locations):
  39     import os
  40     if os.path.isabs(pack):
  41         base = os.path.basename(pack)
  42     else:
  43         base = pack
  44     if _packs.has_key(base):
  45         return
  46     import sys
  47     path = []
  48     for loc in _flatten(locations) + sys.path:
  49         fn = os.path.join(loc, base)
  50         if fn not in path and os.path.isdir(fn):
  51             path.append(fn)
  52     if pack != base and pack not in path and os.path.isdir(pack):
  53         path.append(pack)
  54     if not path: raise ImportError, 'package ' + pack + ' not found'
  55     _packs[base] = path
  56     for fn in path:
  57         if fn not in sys.path:
  58             sys.path.append(fn)
  59
  60 def _flatten(locations):
  61     locs = []
  62     for loc in locations:
  63         if type(loc) == type(''):
  64             locs.append(loc)
  65         else:
  66             locs = locs + _flatten(loc)
  67     return locs