From f0e3569a28bc25cc3a6b267614b9724d8fe01a0e Mon Sep 17 00:00:00 2001
From: Raymond Hettinger <python@rcn.com>
Date: Mon, 8 Mar 2004 05:59:33 +0000
Subject: Refactor the copy dispatcher code in copy.py.  Simplifies and
 shortens the code by grouping common cases together.

---
 Lib/copy.py | 52 +++++++++++++++++-----------------------------------
 1 file changed, 17 insertions(+), 35 deletions(-)

diff --git a/Lib/copy.py b/Lib/copy.py
index 31adfd3..af905f3 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -97,44 +97,26 @@ def copy(x):
 
 _copy_dispatch = d = {}
 
-def _copy_atomic(x):
+def _copy_immutable(x):
     return x
-d[types.NoneType] = _copy_atomic
-d[types.IntType] = _copy_atomic
-d[types.LongType] = _copy_atomic
-d[types.FloatType] = _copy_atomic
-d[types.BooleanType] = _copy_atomic
-try:
-    d[types.ComplexType] = _copy_atomic
-except AttributeError:
-    pass
-d[types.StringType] = _copy_atomic
-try:
-    d[types.UnicodeType] = _copy_atomic
-except AttributeError:
-    pass
-try:
-    d[types.CodeType] = _copy_atomic
-except AttributeError:
-    pass
-d[types.TypeType] = _copy_atomic
-d[types.XRangeType] = _copy_atomic
-d[types.ClassType] = _copy_atomic
-d[types.BuiltinFunctionType] = _copy_atomic
-
-def _copy_list(x):
-    return x[:]
-d[types.ListType] = _copy_list
-
-def _copy_tuple(x):
-    return x[:]
-d[types.TupleType] = _copy_tuple
-
-def _copy_dict(x):
+for t in (types.NoneType, int, long, float, bool, str, tuple,
+          frozenset, type, xrange, types.ClassType,
+          types.BuiltinFunctionType):
+    d[t] = _copy_immutable
+for name in ("ComplexType", "UnicodeType", "CodeType"):
+    t = getattr(types, name, None)
+    if t is not None:
+        d[t] = _copy_immutable
+
+def _copy_with_constructor(x):
+    return type(x)(x)
+for t in (list, dict, set):
+    d[t] = _copy_with_constructor
+
+def _copy_with_copy_method(x):
     return x.copy()
-d[types.DictionaryType] = _copy_dict
 if PyStringMap is not None:
-    d[PyStringMap] = _copy_dict
+    d[PyStringMap] = _copy_with_copy_method
 
 def _copy_inst(x):
     if hasattr(x, '__copy__'):
-- 
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