bpo-36972: Add SupportsIndex (GH-13448)
In order to support typing checks calling hex(), oct() and bin() on user-defined classes, a SupportIndex protocol is required. The ability to check these at runtime would be good to add for completeness sake. This is pretty much just a copy of SupportsInt with the names tweaked.
diff --git a/Doc/library/typing.rst b/Doc/library/typing.rst
index c2523ed..86a3db8 100644
--- a/Doc/library/typing.rst
+++ b/Doc/library/typing.rst
@@ -529,6 +529,12 @@
An ABC with one abstract method ``__bytes__``.
+.. class:: SupportsIndex
+
+ An ABC with one abstract method ``__index__``.
+
+ .. versionadded:: 3.8
+
.. class:: SupportsAbs
An ABC with one abstract method ``__abs__`` that is covariant
diff --git a/Lib/test/test_typing.py b/Lib/test/test_typing.py
index a547fe2..c9bfd0c 100644
--- a/Lib/test/test_typing.py
+++ b/Lib/test/test_typing.py
@@ -568,6 +568,10 @@
self.assertIsSubclass(list, typing.Reversible)
self.assertNotIsSubclass(int, typing.Reversible)
+ def test_supports_index(self):
+ self.assertIsSubclass(int, typing.SupportsIndex)
+ self.assertNotIsSubclass(str, typing.SupportsIndex)
+
def test_protocol_instance_type_error(self):
with self.assertRaises(TypeError):
isinstance(0, typing.SupportsAbs)
diff --git a/Lib/typing.py b/Lib/typing.py
index 530d463..7aab162 100644
--- a/Lib/typing.py
+++ b/Lib/typing.py
@@ -74,6 +74,7 @@
'SupportsBytes',
'SupportsComplex',
'SupportsFloat',
+ 'SupportsIndex',
'SupportsInt',
'SupportsRound',
@@ -1304,6 +1305,14 @@
pass
+class SupportsIndex(_Protocol):
+ __slots__ = ()
+
+ @abstractmethod
+ def __index__(self) -> int:
+ pass
+
+
class SupportsAbs(_Protocol[T_co]):
__slots__ = ()
diff --git a/Misc/ACKS b/Misc/ACKS
index 6b1fdbc..8f0ecb7 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -355,6 +355,7 @@
Raúl Cumplido
Antonio Cuni
Brian Curtin
+Paul Dagnelie
Lisandro Dalcin
Darren Dale
Andrew Dalke
diff --git a/Misc/NEWS.d/next/Library/2019-05-20-17-08-26.bpo-36972.3l3SGc.rst b/Misc/NEWS.d/next/Library/2019-05-20-17-08-26.bpo-36972.3l3SGc.rst
new file mode 100644
index 0000000..da650e8
--- /dev/null
+++ b/Misc/NEWS.d/next/Library/2019-05-20-17-08-26.bpo-36972.3l3SGc.rst
@@ -0,0 +1 @@
+Add SupportsIndex protocol to the typing module to allow type checking to detect classes that can be passed to `hex()`, `oct()` and `bin()`.