Move abc._Abstract into object by adding a new flag Py_TPFLAGS_IS_ABSTRACT,
which forbids constructing types that have it set. The effect is to speed
./python.exe -m timeit -s 'import abc' -s 'class Foo(object): __metaclass__ = abc.ABCMeta' 'Foo()'
up from 2.5us to 0.201us. This fixes issue 1762.
diff --git a/Lib/abc.py b/Lib/abc.py
index 9d15012..5da2590 100644
--- a/Lib/abc.py
+++ b/Lib/abc.py
@@ -51,52 +51,6 @@
__isabstractmethod__ = True
-class _Abstract(object):
-
- """Helper class inserted into the bases by ABCMeta (using _fix_bases()).
-
- You should never need to explicitly subclass this class.
-
- There should never be a base class between _Abstract and object.
- """
-
- def __new__(cls, *args, **kwds):
- am = cls.__dict__.get("__abstractmethods__")
- if am:
- raise TypeError("Can't instantiate abstract class %s "
- "with abstract methods %s" %
- (cls.__name__, ", ".join(sorted(am))))
- if (args or kwds) and cls.__init__ is object.__init__:
- raise TypeError("Can't pass arguments to __new__ "
- "without overriding __init__")
- return super(_Abstract, cls).__new__(cls)
-
- @classmethod
- def __subclasshook__(cls, subclass):
- """Abstract classes can override this to customize issubclass().
-
- This is invoked early on by __subclasscheck__() below. It
- should return True, False or NotImplemented. If it returns
- NotImplemented, the normal algorithm is used. Otherwise, it
- overrides the normal algorithm (and the outcome is cached).
- """
- return NotImplemented
-
-
-def _fix_bases(bases):
- """Helper method that inserts _Abstract in the bases if needed."""
- for base in bases:
- if issubclass(base, _Abstract):
- # _Abstract is already a base (maybe indirectly)
- return bases
- if object in bases:
- # Replace object with _Abstract
- return tuple([_Abstract if base is object else base
- for base in bases])
- # Append _Abstract to the end
- return bases + (_Abstract,)
-
-
class ABCMeta(type):
"""Metaclass for defining Abstract Base Classes (ABCs).
@@ -119,7 +73,6 @@
_abc_invalidation_counter = 0
def __new__(mcls, name, bases, namespace):
- bases = _fix_bases(bases)
cls = super(ABCMeta, mcls).__new__(mcls, name, bases, namespace)
# Compute set of abstract method names
abstracts = set(name
@@ -130,7 +83,7 @@
value = getattr(cls, name, None)
if getattr(value, "__isabstractmethod__", False):
abstracts.add(name)
- cls.__abstractmethods__ = abstracts
+ cls.__abstractmethods__ = frozenset(abstracts)
# Set up inheritance registry
cls._abc_registry = set()
cls._abc_cache = set()