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gh-100239: specialize bytes binary operations by Wulian233 · Pull Request #149458 · python/cpython · GitHub

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gh-100239: specialize bytes binary operations - #149458

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Wulian233 wants to merge 2 commits into
python:mainfrom
Wulian233:bytes
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gh-100239: specialize bytes binary operations#149458
Wulian233 wants to merge 2 commits into
python:mainfrom
Wulian233:bytes

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Wulian233 commented May 6, 2026 •
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The following was generated by Codex:

  • bytes[3]: 20,000,000 iterations
  • 7 repeats
  • PYTHON_UOPS_OPTIMIZE=0
  • compared normal specialization vs PYTHON_SPECIALIZATION_OFF=1

Results:

Benchmark Specialized median Unspecialized median Speedup
bytes[3] 0.513025s 0.701673s ~26.9% faster
Details 
import statistics
import time

N = 20_000_000
REPEAT = 7


def bench_bytes_index():
    b = b"foobar"
    x = 0
    for _ in range(N):
        x = b[3]
    return x


# Warm up for specialization.
for _ in range(5):
    bench_bytes_index()

samples = []
for _ in range(REPEAT):
    t0 = time.perf_counter()
    result = bench_bytes_index()
    samples.append(time.perf_counter() - t0)

print("result", result)
print("samples", " ".join(f"{s:.6f}" for s in samples))
print("median", f"{statistics.median(samples):.6f}")

bedevere-app Bot mentioned this pull request May 6, 2026
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eendebakpt reviewed May 6, 2026
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Comment thread Python/specialize.c Outdated
Comment thread Python/specialize.c Outdated
}

static PyObject *
bytes_slice_subscr(PyObject *lhs, PyObject *rhs)

eendebakpt May 6, 2026

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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

The implementation here is seems copied from bytes_subscript (in byteobject.c) and still has a large overlap. Can you refactor the bytes_subscript into multiple methods so that the method here only becomes a very thin wrapper?

StanFromIreland reviewed May 6, 2026
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corona10 reviewed May 6, 2026
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Choose a reason Spam Abuse Off Topic Outdated Duplicate Resolved Low Quality

I am not sure we actually need this specialization. Is there any metrics that that this operation is executed frequently in performance benchmark.
We can add tons of specialization it we want, but IIUC, we just pick few of them.

eendebakpt commented May 7, 2026

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I am not sure we actually need this specialization. Is there any metrics that that this operation is executed frequently in performance benchmark. We can add tons of specialization it we want, but IIUC, we just pick few of them.

I agree we should limit the number of specializations. The bytes indexing seems worthwhile atm, the bytes slicing not so much.

Another option: reconsider an extension mechanism. It was implemented once and reverted (because of a python release date and some technical worries): #133395. If we can get similar performance improvements with the extension mechanism, when we can leave which ops to specialize to the user and outside cpython.

read-the-docs-community Bot commented May 7, 2026

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Documentation build overview

📚 cpython-previews | 🛠️ Build #32582538 | 📁 Comparing c7dfa59 against main (b3cfd36)

  🔍 Preview build  

26 files changed · ± 26 modified

± Modified

Wulian233 closed this May 24, 2026
Wulian233 deleted the bytes branch May 24, 2026 07:47
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