Adding a short script that I've found useful many times over the past decade. It has allowed my to quickly notice performance regressions and has helped identify places in need of optimization work. It is also useful for building a empirical mental model of the relative cost of various kinds of variable access -- this is useful in writing high performance code.

Here's what the output looks like (here am comparing a fresh Py3.8 with Clang versus the same build with GCC-8): $ make distclean && ./configure && make $ py Tools/scripts/var_access_benchmark.py Speed of different kinds of variable accesses: 4.2 μs	read_local 4.7 μs	read_nonlocal 13.7 μs	read_global 18.5 μs	read_builtin 18.2 μs	read_classvar 26.8 μs	read_instancevar 20.3 μs	read_instancevar_slots 19.1 μs	read_namedtuple 26.9 μs	read_boundmethod 4.5 μs	write_local 4.8 μs	write_nonlocal 18.8 μs	write_global 89.9 μs	write_classvar 37.1 μs	write_instancevar 25.7 μs	write_instancevar_slots 0.3 μs	loop_overhead $ make distclean && ./configure CC=gcc-8 && make $ py Tools/scripts/var_access_benchmark.py Speed of different kinds of variable accesses: 4.0 μs	read_local 4.2 μs	read_nonlocal 11.4 μs	read_global 16.3 μs	read_builtin 16.4 μs	read_classvar 24.8 μs	read_instancevar 20.1 μs	read_instancevar_slots 16.8 μs	read_namedtuple 23.2 μs	read_boundmethod 4.3 μs	write_local 4.5 μs	write_nonlocal 15.4 μs	write_global 89.4 μs	write_classvar 33.5 μs	write_instancevar 24.5 μs	write_instancevar_slots 0.3 μs	loop_overhead

 New changeset f75d59e1a896115bd52f543a417c665d6edc331f by Raymond Hettinger in branch 'master': bpo-35884: Add variable access benchmarking script (GH-11725) https://github.com/python/cpython/commit/f75d59e1a896115bd52f543a417c665d6edc331f 

 New changeset 43766f82ddec84fad7a321eeec2e1cbff6ee44d2 by Miss Islington (bot) (Raymond Hettinger) in branch 'master': bpo-35884: Add missing FIFO queue benchmark (GH-11898) https://github.com/python/cpython/commit/43766f82ddec84fad7a321eeec2e1cbff6ee44d2 

 New changeset 68d228f174ceed151200e7e0b44ffc5edd4e0ea2 by Raymond Hettinger (Stefan Behnel) in branch 'master': bpo-35884: Add string-keys-only microbenchmark for dict access to var_access_benchmark.py (GH-11905) https://github.com/python/cpython/commit/68d228f174ceed151200e7e0b44ffc5edd4e0ea2