itertools: fix count() repr to show float step 1.0

[JaceJung-dev]

• This PR follows our AI policy.

Summary

itertools.count()'s __repr__ omitted the step when it equalled 1, but
CPython omits the step only for the integer 1 — a float step of 1.0
should still be shown.

from itertools import count
repr(count(10.5))
# before: 'count(10.5)'
# after:  'count(10.5, 1.0)'   # matches CPython

CPython's count_repr skips the step only when it is a PyLong equal to 1,
so a float such as 1.0 is still shown. The repr now omits the step only when it
is exactly the integer 1 (checked via both the int type and value). Also
unmarks test_count_with_step, which now passes.

Verified locally:

• cargo run --release -- -m unittest -v test.test_itertools.TestBasicOps.test_count_with_step -> ok
• cargo run --release -- -m test test_itertools -> SUCCESS (run=137, skipped=22)

Assisted-by: Claude Code:claude-opus-4-8

Summary by CodeRabbit

• Bug Fixes
  • Improved the display of iterator count expressions.
  • The step value is now omitted only when it is exactly the integer 1; other values and types remain explicitly shown for accurate representations.

[coderabbitai]

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📥 Commits

Reviewing files that changed from the base of the PR and between d9f76ac and 51b83c4.

⛔ Files ignored due to path filters (1)

• Lib/test/test_itertools.py is excluded by !Lib/**

📒 Files selected for processing (1)

• crates/vm/src/stdlib/itertools.rs

🚧 Files skipped from review as they are similar to previous changes (1)

• crates/vm/src/stdlib/itertools.rs

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📝 Walkthrough

Walkthrough

PyItertoolsCount::repr_wtf8 precomputes whether step is an integer equal to one, then uses that predicate to decide whether to include step in the count(...) representation.

Changes

Count representation

Layer / File(s)	Summary
Step formatting predicate crates/vm/src/stdlib/itertools.rs	repr_wtf8 checks the step type and equality with 1 before omitting the step from the count(...) representation.

Estimated code review effort: 1 (Trivial) | ~3 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title accurately describes the main change: count() repr now includes a float step like 1.0 instead of omitting it.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

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• Create PR with unit tests

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[github-actions]

📦 Library Dependencies

The following Lib/ modules were modified. Here are their dependencies:

[x] test: cpython/Lib/test/test_itertools.py (TODO: 6)

dependencies:

dependent tests: (56 tests)

• itertools: test_annotationlib test_ast test_asyncio test_bdb test_buffer test_builtin test_call test_codeccallbacks test_collections test_compile test_concurrent_futures test_csv test_ctypes test_descr test_dis test_email test_exceptions test_functools test_genericalias test_hashlib test_heapq test_httplib test_importlib test_inspect test_io test_iterlen test_itertools test_launcher test_logging test_math test_memoryview test_mmap test_os test_peepholer test_platform test_pprint test_pyrepl test_queue test_range test_set test_shlex test_slice test_socket test_sort test_statistics test_str test_struct test_subprocess test_tokenize test_tuple test_typing test_unittest test_uuid test_winreg test_xml_etree test_zipfile

Legend:

• [+] path exists in CPython
• [x] up-to-date, [ ] outdated

[moreal]

Hello, it looks like your changes correspond to these lines:

https://github.com/python/cpython/blob/c63aec69bd59c55314c06c23f4c22c03de76fe45/Modules/itertoolsmodule.c#L3555-L3569

Everything seems to pass the tests on my local machine (cargo run -- -m test test_itertools -m test_count_with_step -v), so I'm leaving an approval. Thanks for your contribution!

However, the CI is currently failing. I believe rebasing onto the latest main branch should resolve this issue.

[JaceJung-dev]

Thanks for the review and approval! 🙏
I've rebased onto the latest main(which includes the clippy fix in #8249) to resolve the CI failure.
Thanks for the helpful guidance — much appreciated!

[ShaharNaveh]

tysm!