Add initial implementation of importlib. See the NOTES files for what is

planned for the package.

There are no docs yet, but they are coming once the API for the first new
function, importlib.import_module() is finalized.

Lib/importlib/__init__.py

@@ -0,0 +1,133 @@
+"""A pure Python implementation of import.
+
+References on import:
+
+    * Language reference
+          http://docs.python.org/ref/import.html
+    * __import__ function
+          http://docs.python.org/lib/built-in-funcs.html
+    * Packages
+          http://www.python.org/doc/essays/packages.html
+    * PEP 235: Import on Case-Insensitive Platforms
+          http://www.python.org/dev/peps/pep-0235
+    * PEP 275: Import Modules from Zip Archives
+          http://www.python.org/dev/peps/pep-0273
+    * PEP 302: New Import Hooks
+          http://www.python.org/dev/peps/pep-0302/
+    * PEP 328: Imports: Multi-line and Absolute/Relative
+          http://www.python.org/dev/peps/pep-0328
+
+"""
+from . import _bootstrap
+
+# XXX Temporary functions that should eventually be removed.
+import os
+import re
+import tokenize
+
+def _set__import__():
+    """Set __import__ to an instance of Import."""
+    global original__import__
+    original__import__ = __import__
+    __builtins__['__import__'] = Import()
+
+
+def _reset__import__():
+    """Set __import__ back to the original implementation (assumes
+    _set__import__ was called previously)."""
+    __builtins__['__import__'] = original__import__
+
+
+def _case_ok(directory, check):
+    """Check if the directory contains something matching 'check'.
+
+    No check is done if the file/directory exists or not.
+
+    """
+    if 'PYTHONCASEOK' in os.environ:
+        return True
+    elif check in os.listdir(directory):
+        return True
+    return False
+
+
+def _w_long(x):
+    """Convert a 32-bit integer to little-endian.
+
+    XXX Temporary until marshal's long functions are exposed.
+
+    """
+    x = int(x)
+    int_bytes = []
+    int_bytes.append(x & 0xFF)
+    int_bytes.append((x >> 8) & 0xFF)
+    int_bytes.append((x >> 16) & 0xFF)
+    int_bytes.append((x >> 24) & 0xFF)
+    return bytearray(int_bytes)
+
+
+def _r_long(int_bytes):
+    """Convert 4 bytes in little-endian to an integer.
+
+    XXX Temporary until marshal's long function are exposed.
+
+    """
+    x = int_bytes[0]
+    x |= int_bytes[1] << 8
+    x |= int_bytes[2] << 16
+    x |= int_bytes[3] << 24
+    return x
+
+
+def import_module(name, package=None):
+    """Import a module.
+
+    The 'package' argument is used to resolve relative import names. Typically
+    this is the __package__ attribute of the module making the function call.
+
+    """
+    if name.startswith('.'):
+        if not package:
+            raise TypeError("relative imports require the 'package' argument")
+        level = 0
+        for character in name:
+            if character != '.':
+                break
+            level += 1
+        name = Import._resolve_name(name[level:], package, level)
+    __import__(name)
+    return sys.modules[name]
+
+
+
+# Required built-in modules.
+try:
+    import posix as _os
+except ImportError:
+    try:
+        import nt as _os
+    except ImportError:
+        try:
+            import os2 as _os
+        except ImportError:
+            raise ImportError('posix, nt, or os2 module required for importlib')
+_bootstrap._os = _os
+import imp, sys, marshal, errno, _fileio
+_bootstrap.imp = imp
+_bootstrap.sys = sys
+_bootstrap.marshal = marshal
+_bootstrap.errno = errno
+_bootstrap._fileio = _fileio
+import _warnings
+_bootstrap._warnings = _warnings
+
+
+from os import sep
+# For os.path.join replacement; pull from Include/osdefs.h:SEP .
+_bootstrap.path_sep = sep
+
+_bootstrap._case_ok = _case_ok
+marshal._w_long = _w_long
+marshal._r_long = _r_long
+
+from ._bootstrap import *