Demo/imputil/knee.py

   1 """An Python re-implementation of hierarchical module import.
   2
   3 This code is intended to be read, not executed.  However, it does work
   4 -- all you need to do to enable it is "import knee".
   5
   6 (The name is a pun on the klunkier predecessor of this module, "ni".)
   7
   8 """
   9
  10 import sys, imp, __builtin__
  11
  12
  13 # Replacement for __import__()
  14 def import_hook(name, globals=None, locals=None, fromlist=None):
  15     parent = determine_parent(globals)
  16     q, tail = find_head_package(parent, name)
  17     m = load_tail(q, tail)
  18     if not fromlist:
  19         return q
  20     if hasattr(m, "__path__"):
  21         ensure_fromlist(m, fromlist)
  22     return m
  23
  24 def determine_parent(globals):
  25     if not globals or  not globals.has_key("__name__"):
  26         return None
  27     pname = globals['__name__']
  28     if globals.has_key("__path__"):
  29         parent = sys.modules[pname]
  30         assert globals is parent.__dict__
  31         return parent
  32     if '.' in pname:
  33         i = pname.rfind('.')
  34         pname = pname[:i]
  35         parent = sys.modules[pname]
  36         assert parent.__name__ == pname
  37         return parent
  38     return None
  39
  40 def find_head_package(parent, name):
  41     if '.' in name:
  42         i = name.find('.')
  43         head = name[:i]
  44         tail = name[i+1:]
  45     else:
  46         head = name
  47         tail = ""
  48     if parent:
  49         qname = "%s.%s" % (parent.__name__, head)
  50     else:
  51         qname = head
  52     q = import_module(head, qname, parent)
  53     if q: return q, tail
  54     if parent:
  55         qname = head
  56         parent = None
  57         q = import_module(head, qname, parent)
  58         if q: return q, tail
  59     raise ImportError, "No module named " + qname
  60
  61 def load_tail(q, tail):
  62     m = q
  63     while tail:
  64         i = tail.find('.')
  65         if i < 0: i = len(tail)
  66         head, tail = tail[:i], tail[i+1:]
  67         mname = "%s.%s" % (m.__name__, head)
  68         m = import_module(head, mname, m)
  69         if not m:
  70             raise ImportError, "No module named " + mname
  71     return m
  72
  73 def ensure_fromlist(m, fromlist, recursive=0):
  74     for sub in fromlist:
  75         if sub == "*":
  76             if not recursive:
  77                 try:
  78                     all = m.__all__
  79                 except AttributeError:
  80                     pass
  81                 else:
  82                     ensure_fromlist(m, all, 1)
  83             continue
  84         if sub != "*" and not hasattr(m, sub):
  85             subname = "%s.%s" % (m.__name__, sub)
  86             submod = import_module(sub, subname, m)
  87             if not submod:
  88                 raise ImportError, "No module named " + subname
  89
  90 def import_module(partname, fqname, parent):
  91     try:
  92         return sys.modules[fqname]
  93     except KeyError:
  94         pass
  95     try:
  96         fp, pathname, stuff = imp.find_module(partname,
  97                                               parent and parent.__path__)
  98     except ImportError:
  99         return None
 100     try:
 101         m = imp.load_module(fqname, fp, pathname, stuff)
 102     finally:
 103         if fp: fp.close()
 104     if parent:
 105         setattr(parent, partname, m)
 106     return m
 107
 108
 109 # Replacement for reload()
 110 def reload_hook(module):
 111     name = module.__name__
 112     if '.' not in name:
 113         return import_module(name, name, None)
 114     i = name.rfind('.')
 115     pname = name[:i]
 116     parent = sys.modules[pname]
 117     return import_module(name[i+1:], name, parent)
 118
 119
 120 # Save the original hooks
 121 original_import = __builtin__.__import__
 122 original_reload = __builtin__.reload
 123
 124 # Now install our hooks
 125 __builtin__.__import__ = import_hook
 126 __builtin__.reload = reload_hook