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

Miss Islington (bot) webhook-mailer at python.org
Sun Jan 12 13:00:31 EST 2020

commit: 4be97260351f214d3c8b8477682323bb52ee2af3
branch: 3.7
author: Miss Islington (bot) <31488909+miss-islington at users.noreply.github.com>
committer: GitHub <noreply at github.com>
date: 2020-01-12T10:00:27-08:00

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 :)

(cherry picked from commit 9f3fc6c5b4993f2b362263b494f84793a21aa073)

Co-authored-by: Guðni Natan Gunnarsson <1493259+GudniNatan at users.noreply.github.com>

A Misc/NEWS.d/next/Library/2019-09-29-08-17-03.bpo-38293.wls5s3.rst
M Lib/copy.py
M Lib/test/test_copy.py

diff --git a/Lib/copy.py b/Lib/copy.py
index f86040a33c554..e634c43e347b9 100644
--- a/Lib/copy.py
+++ b/Lib/copy.py
@@ -111,7 +111,7 @@ def copy(x):
 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
@@ -206,6 +206,7 @@ def _deepcopy_atomic(x, memo):
 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 = []
diff --git a/Lib/test/test_copy.py b/Lib/test/test_copy.py
index 45a692022f29b..35f72fb216b64 100644
--- a/Lib/test/test_copy.py
+++ b/Lib/test/test_copy.py
@@ -99,7 +99,7 @@ class WithMetaclass(metaclass=abc.ABCMeta):
                  42, 2**100, 3.14, True, False, 1j,
                  "hello", "hello\u1234", f.__code__,
                  b"world", bytes(range(256)), range(10), slice(1, 10, 2),
-                 NewStyle, Classic, max, WithMetaclass]
+                 NewStyle, Classic, max, WithMetaclass, property()]
         for x in tests:
             self.assertIs(copy.copy(x), x)
@@ -357,7 +357,7 @@ def f():
         tests = [None, 42, 2**100, 3.14, True, False, 1j,
                  "hello", "hello\u1234", f.__code__,
-                 NewStyle, Classic, max]
+                 NewStyle, Classic, max, property()]
         for x in tests:
             self.assertIs(copy.deepcopy(x), x)
diff --git a/Misc/NEWS.d/next/Library/2019-09-29-08-17-03.bpo-38293.wls5s3.rst b/Misc/NEWS.d/next/Library/2019-09-29-08-17-03.bpo-38293.wls5s3.rst
new file mode 100644
index 0000000000000..0b19551970eb0
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-09-29-08-17-03.bpo-38293.wls5s3.rst
@@ -0,0 +1 @@
+Add :func:`copy.copy` and :func:`copy.deepcopy` support to :func:`property` objects.
\ No newline at end of file

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