ham[lower+offset : upper+offset]
ham[:upper_fn(x) : step_fn(x)], ham[:: step_fn(x)]
ham[lower + offset : upper + offset]
becomes:
ham[lower + offset:upper + offset]
ham[:upper_fn(x):step_fn(x)], ham[::step_fn(x)]
ham[lower + offset:upper + offset]
Taken from PEP 8 in it's "pet peeves" section.