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Adding fastpath for Nonetype in PyUnicodeWriter_WriteRepr #159813
Description
According to metric in #159702 (comment), NoneType occupied 5%, so it's worth to adding this fast path rather than other type if we have to do.
Metric
| Argument type | Calls | Share | Note |
|---|---|---|---|
| exact int | 2,924,088 | 86.7% | existing fast path (_PyLong_FormatWriter) |
| None | 181,066 | 5.4% | proposed fastpath |
| exact list | 69,501 | 2.1% | |
| other types | 58,946 | 1.7% | user classes, type objects, etc. |
| exact str | 58,158 | 1.7% | |
| exact dict | 40,537 | 1.2% | |
| bool | 20,759 | 0.6% | |
| exact float | 10,657 | 0.32% | |
| exact bytes | 5,700 | 0.2% | |
| exact tuple | 2,244 | 0.07% | |
| total | 3,371,663 | 100% |
Microbenchmark
import pyperf
runner = pyperf.Runner()
for n in (10, 100, 1000):
runner.bench_func(f"repr([None]*{n})", repr, [None] * n)+-------------------+------------------+-----------------------+ | Benchmark | wr_none_baseline | wr_none_patched | +===================+==================+=======================+ | repr([None]*10) | 559 ns | 234 ns: 2.39x faster | +-------------------+------------------+-----------------------+ | repr([None]*100) | 3.90 us | 1.10 us: 3.53x faster | +-------------------+------------------+-----------------------+ | repr([None]*1000) | 36.9 us | 9.50 us: 3.88x faster | +-------------------+------------------+-----------------------+ | Geometric mean | (ref) | 3.20x faster | +-------------------+------------------+-----------------------+
Activity
corona10 commented on Oct 19, 2026
cc @vstinner @nineteendo
pythongh-159813: Add tests for PyUnicodeWriter_WriteRepr()
gh-159813: Add a fast path for None in PyUnicodeWriter_WriteRepr (gh-…