import pyperf
runner = pyperf.Runner()

setup="""
d = {ii: ii+1 for ii in range(200)}
dct_items = d.items()
"""
runner.timeit(name="extend list with dict keys", stmt="l = []; l += d", setup=setup)
runner.timeit(name="extend list with dict items", stmt="l = []; l += dct_items", setup=setup)

extend list with dict items: Mean +- std dev: [main] 3.78 us +- 0.07 us -> [pr] 3.17 us +- 0.03 us: 1.19x faster

Benchmark hidden because not significant (1): extend list with dict keys

Geometric mean: 1.09x faster