Performance of attribute lookup for type objects · Issue #92216 · python/cpython (original) (raw)

The performance of attribute lookup for type objects is worse than for other objects. A benchmark

import pyperf
runner=pyperf.Runner()

setup="""
class Class:
    def all(self):
        pass

x=Class()
"""

runner.timeit('hasattr x.all', "hasattr(x, 'all')", setup=setup)
runner.timeit('hasattr x.__array_ufunc__', "hasattr(x, '__array_ufunc__')", setup=setup)
runner.timeit('hasattr Class.all', "hasattr(Class, 'all')", setup=setup)
runner.timeit('hasattr Class.__array_ufunc__', "hasattr(Class, '__array_ufunc__')", setup=setup) # worse performance

hasattr x.all: Mean +- std dev: 68.1 ns +- 1.1 ns
hasattr x.__array_ufunc__: Mean +- std dev: 40.4 ns +- 0.3 ns
hasattr Class.all: Mean +- std dev: 38.1 ns +- 0.6 ns
hasattr Class.__array_ufunc__: Mean +- std dev: 255 ns +- 2 ns

The reason seems to be that the type_getattro always executes PyErr_Format, wheras for the "normal" attribute lookup this is avoided (see here and here)