bpo-38293: Allow shallow and deep copying of property objects (GH-16438)

Copying property objects results in a TypeError. Steps to reproduce:

```
>>> import copy
>>> obj = property()
>>> copy.copy(obj)
````

This affects both shallow and deep copying.  
My idea for a fix is to add property objects to the list of "atomic" objects in the copy module.
These already include types like functions and type objects.

I also added property objects to the unit tests test_copy_atomic and test_deepcopy_atomic. This is my first PR, and it's highly likely I've made some mistake, so please be kind :)


https://bugs.python.org/issue38293

1 files changed, 2 insertions, 1 deletions

diff --git a/Lib/copy.py b/Lib/copy.py
index f53cd8c..41873f2 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -107,7 +107,7 @@ _copy_dispatch = d = {}
 def _copy_immutable(x):
     return x
 for t in (type(None), int, float, bool, complex, str, tuple,
-          bytes, frozenset, type, range, slice,
+          bytes, frozenset, type, range, slice, property,
           types.BuiltinFunctionType, type(Ellipsis), type(NotImplemented),
           types.FunctionType, weakref.ref):
     d[t] = _copy_immutable
@@ -195,6 +195,7 @@ d[type] = _deepcopy_atomic
 d[types.BuiltinFunctionType] = _deepcopy_atomic
 d[types.FunctionType] = _deepcopy_atomic
 d[weakref.ref] = _deepcopy_atomic
+d[property] = _deepcopy_atomic
 
 def _deepcopy_list(x, memo, deepcopy=deepcopy):
     y = []