1 files changed, 95 insertions, 0 deletions
diff --git a/paste/util/import_string.py b/paste/util/import_string.py
new file mode 100644
index 0000000..a10db18
--- /dev/null
+++ b/paste/util/import_string.py
@@ -0,0 +1,95 @@
+# (c) 2005 Ian Bicking and contributors; written for Paste (http://pythonpaste.org)
+# Licensed under the MIT license: http://www.opensource.org/licenses/mit-license.php
+
+"""
+'imports' a string -- converts a string to a Python object, importing
+any necessary modules and evaluating the expression.  Everything
+before the : in an import expression is the module path; everything
+after is an expression to be evaluated in the namespace of that
+module.
+
+Alternately, if no : is present, then import the modules and get the
+attributes as necessary.  Arbitrary expressions are not allowed in
+that case.
+"""
+
+def eval_import(s):
+    """
+    Import a module, or import an object from a module.
+
+    A module name like ``foo.bar:baz()`` can be used, where
+    ``foo.bar`` is the module, and ``baz()`` is an expression
+    evaluated in the context of that module.  Note this is not safe on
+    arbitrary strings because of the eval.
+    """
+    if ':' not in s:
+        return simple_import(s)
+    module_name, expr = s.split(':', 1)
+    module = import_module(module_name)
+    obj = eval(expr, module.__dict__)
+    return obj
+
+def simple_import(s):
+    """
+    Import a module, or import an object from a module.
+
+    A name like ``foo.bar.baz`` can be a module ``foo.bar.baz`` or a
+    module ``foo.bar`` with an object ``baz`` in it, or a module
+    ``foo`` with an object ``bar`` with an attribute ``baz``.
+    """
+    parts = s.split('.')
+    module = import_module(parts[0])
+    name = parts[0]
+    parts = parts[1:]
+    last_import_error = None
+    while parts:
+        name += '.' + parts[0]
+        try:
+            module = import_module(name)
+            parts = parts[1:]
+        except ImportError as e:
+            last_import_error = e
+            break
+    obj = module
+    while parts:
+        try:
+            obj = getattr(module, parts[0])
+        except AttributeError:
+            raise ImportError(
+                "Cannot find %s in module %r (stopped importing modules with error %s)" % (parts[0], module, last_import_error))
+        parts = parts[1:]
+    return obj
+
+def import_module(s):
+    """
+    Import a module.
+    """
+    mod = __import__(s)
+    parts = s.split('.')
+    for part in parts[1:]:
+        mod = getattr(mod, part)
+    return mod
+
+def try_import_module(module_name):
+    """
+    Imports a module, but catches import errors.  Only catches errors
+    when that module doesn't exist; if that module itself has an
+    import error it will still get raised.  Returns None if the module
+    doesn't exist.
+    """
+    try:
+        return import_module(module_name)
+    except ImportError as e:
+        if not getattr(e, 'args', None):
+            raise
+        desc = e.args[0]
+        if not desc.startswith('No module named '):
+            raise
+        desc = desc[len('No module named '):]
+        # If you import foo.bar.baz, the bad import could be any
+        # of foo.bar.baz, bar.baz, or baz; we'll test them all:
+        parts = module_name.split('.')
+        for i in range(len(parts)):
+            if desc == '.'.join(parts[i:]):
+                return None
+        raise