circuitpython/tests/basics/builtin_property_inherit.py

54 lines
1.0 KiB
Python
Raw Normal View History

py/objtype: Optimise instance get/set/del by skipping special accessors. This patch is a code optimisation, trading text bytes for speed. On pyboard it's an increase of 0.06% in code size for a gain (in pystone performance) of roughly 6.5%. The patch optimises load/store/delete of attributes in user defined classes by not looking up special accessors (@property, __get__, __delete__, __set__, __setattr__ and __getattr_) if they are guaranteed not to exist in the class. Currently, if you do my_obj.foo() then the runtime has to do a few checks to see if foo is a property or has __get__, and if so delegate the call. And for stores things like my_obj.foo = 1 has to first check if foo is a property or has __set__ defined on it. Doing all those checks each and every time the attribute is accessed has a performance penalty. This patch eliminates all those checks for cases when it's guaranteed that the checks will always fail, ie no attributes are properties nor have any special accessor methods defined on them. To make this guarantee it checks all attributes of a user-defined class when it is first created. If any of the attributes of the user class are properties or have special accessors, or any of the base classes of the user class have them, then it sets a flag in the class to indicate that special accessors must be checked for. Then in the load/store/delete code it checks this flag to see if it can take the shortcut and optimise the lookup. It's an optimisation that's pretty widely applicable because it improves lookup performance for all methods of user defined classes, and stores of attributes, at least for those that don't have special accessors. And, it allows to enable descriptors with minimal additional runtime overhead if they are not used for a particular user class. There is one restriction on dynamic class creation that has been introduced by this patch: a user-defined class cannot go from zero special accessors to one special accessor (or more) after that class has been subclassed. If the script attempts this an AttributeError is raised (see addition to tests/misc/non_compliant.py for an example of this case). The cost in code space bytes for the optimisation in this patch is: unix x64: +528 unix nanbox: +508 stm32: +192 cc3200: +200 esp8266: +332 esp32: +244 Performance tests that were done: - on unix x86-64, pystone improved by about 5% - on pyboard, pystone improved by about 6.5%, from 1683 up to 1794 - on pyboard, bm_chaos (from CPython benchmark suite) improved by about 5% - on esp32, pystone improved by about 30% (but there are caching effects) - on esp32, bm_chaos improved by about 11%
2018-05-25 03:09:54 -04:00
# test builtin property combined with inheritance
try:
property
except:
print("SKIP")
raise SystemExit
# test property in a base class works for derived classes
class A:
@property
def x(self):
print('A x')
return 123
class B(A):
pass
class C(B):
pass
class D:
pass
class E(C, D):
pass
print(A().x)
print(B().x)
print(C().x)
print(E().x)
# test that we can add a property to base class after creation
class F:
pass
F.foo = property(lambda self: print('foo get'))
class G(F):
pass
F().foo
G().foo
# should be able to add a property to already-subclassed class because it already has one
F.bar = property(lambda self: print('bar get'))
F().bar
G().bar
# test case where class (H here) is already subclassed before adding attributes
class H:
pass
class I(H):
pass
# should be able to add a normal member to already-subclassed class
H.val = 2
print(I().val)
# should be able to add a property to the derived class
I.baz = property(lambda self: print('baz get'))
I().baz