beginning to build the revision system

1 files changed, 23 insertions, 0 deletions

diff --git a/alembic/util.py b/alembic/util.py
index 88085ee..df5bfd8 100644
--- a/alembic/util.py
+++ b/alembic/util.py
@@ -3,6 +3,7 @@ import sys
 import os
 import textwrap
 from sqlalchemy import util
+import imp
 
 NO_VALUE = util.symbol("NO_VALUE")
 
@@ -40,3 +41,25 @@ def msg(msg, newline=True):
         for line in lines[0:-1]:
             sys.stdout.write("  " +line + "\n")
     sys.stdout.write("  " + lines[-1] + ("\n" if newline else ""))
+
+def load_python_file(dir_, filename):
+    """Load a file from the given path as a Python module."""
+    
+    module_id = re.sub(r'\W', "_", filename)
+    path = os.path.join(dir_, filename)
+    module = imp.load_source(module_id, path, open(path, 'rb'))
+    del sys.modules[module_id]
+    return module
+
+class memoized_property(object):
+    """A read-only @property that is only evaluated once."""
+    def __init__(self, fget, doc=None):
+        self.fget = fget
+        self.__doc__ = doc or fget.__doc__
+        self.__name__ = fget.__name__
+
+    def __get__(self, obj, cls):
+        if obj is None:
+            return None
+        obj.__dict__[self.__name__] = result = self.fget(obj)
+        return result