1 files changed, 59 insertions, 0 deletions
diff --git a/lib/sqlalchemy/sql/_py_util.py b/lib/sqlalchemy/sql/_py_util.py
new file mode 100644
index 000000000..ceb637609
--- /dev/null
+++ b/lib/sqlalchemy/sql/_py_util.py
@@ -0,0 +1,59 @@
+# sql/_py_util.py
+# Copyright (C) 2005-2021 the SQLAlchemy authors and contributors
+# <see AUTHORS file>
+#
+# This module is part of SQLAlchemy and is released under
+# the MIT License: https://www.opensource.org/licenses/mit-license.php
+
+
+class prefix_anon_map(dict):
+    """A map that creates new keys for missing key access.
+
+    Considers keys of the form "<ident> <name>" to produce
+    new symbols "<name>_<index>", where "index" is an incrementing integer
+    corresponding to <name>.
+
+    Inlines the approach taken by :class:`sqlalchemy.util.PopulateDict` which
+    is otherwise usually used for this type of operation.
+
+    """
+
+    def __missing__(self, key):
+        (ident, derived) = key.split(" ", 1)
+        anonymous_counter = self.get(derived, 1)
+        self[derived] = anonymous_counter + 1
+        value = f"{derived}_{anonymous_counter}"
+        self[key] = value
+        return value
+
+
+class cache_anon_map(dict):
+    """A map that creates new keys for missing key access.
+
+    Produces an incrementing sequence given a series of unique keys.
+
+    This is similar to the compiler prefix_anon_map class although simpler.
+
+    Inlines the approach taken by :class:`sqlalchemy.util.PopulateDict` which
+    is otherwise usually used for this type of operation.
+
+    """
+
+    _index = 0
+
+    def get_anon(self, object_):
+
+        idself = id(object_)
+        if idself in self:
+            return self[idself], True
+        else:
+            # inline of __missing__
+            self[idself] = id_ = str(self._index)
+            self._index += 1
+
+            return id_, False
+
+    def __missing__(self, key):
+        self[key] = val = str(self._index)
+        self._index += 1
+        return val