What is there

count, cycle, repeat, accumulate (func=, initial=), chain, from_iterable, compress, dropwhile, takewhile, filterfalse, groupby (key=), islice (1-3 bounds), starmap, tee, zip_longest (fillvalue=), pairwise, product (repeat=), permutations, combinations, combinations_with_replacement. batched (3.12) is absent.

Divergences, in the shim's docstring: groupby yields each group as a LIST; tee materialises its input; chain.from_iterable is spelled from_iterable at module level; starmap spreads at most four arguments.

What it took

Writing the shim surfaced five compiler bugs, all fixed the same day, each with its own done ticket:

• bug-n-a-for-over-a-variant-drains-a-generator-before-the-first-iteration
• bug-n-a-module-qualified-generator-call-is-called-not-built
• bug-n-a-def-returning-a-generator-call-is-typed-bool
• bug-n-a-generator-does-not-hold-a-reference-to-its-object-arguments
• bug-n-next-on-an-untyped-value-binds-the-old-counter-overload

Verified

test/test_nilpy_mimic_itertools.npy: every function, both import spellings, output byte-identical to CPython 3, under -dPXX_HEAP_DEBUG and on i386.