python / python/cpython

`LOAD_SMALL_INT` has empty `argrepr` via `Bytecode`

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stdlib type-bug
Dominant language
Python
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Description

Bug report

Bug description:

When using Bytecode to disassemble some Python code I've noticed that the argrepr attribute of the Instruction holding a LOAD_SMALL_INT isn't populated. For example:

Python 3.14.0 (main, Oct 16 2025, 09:17:39) [Clang 17.0.0 (clang-1700.3.19.1)] on darwin
Type "help", "copyright", "credits" or "license" for more information.
>>> from dis import Bytecode
>>> list(Bytecode("1"))
[
    Instruction(
        opname='RESUME',
        opcode=128,
        arg=0,
        argval=0,
        argrepr='',
        offset=0,
        start_offset=0,
        starts_line=True,
        line_number=0,
        label=None,
        positions=Positions(lineno=0, end_lineno=1, col_offset=0, end_col_offset=0),
        cache_info=None
    ),
    Instruction(
        opname='LOAD_SMALL_INT',
        opcode=94,
        arg=1,
        argval=1,
        argrepr='',     # <--- Empty string
        offset=2,
        start_offset=2,
        starts_line=True,
        line_number=1,
        label=None,
        positions=Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=1),
        cache_info=None
    ),
    Instruction(
        opname='RETURN_VALUE',
        opcode=35,
        arg=None,
        argval=None,
        argrepr='',
        offset=4,
        start_offset=4,
        starts_line=False,
        line_number=1,
        label=None,
        positions=Positions(lineno=1, end_lineno=1, col_offset=0, end_col_offset=1),
        cache_info=None
    )
]

I would have expected this to have the repr of the argument in there.

A quick and ignorant reading of dis.py suggests to me that there should be a change akin to this:

--- ../cpython/Lib/dis.py       2025-10-17 14:31:35.495151419 +0100
+++ my/dis.py   2025-10-17 14:43:26.650409153 +0100
@@ -586,7 +586,7 @@
             #    _disassemble_bytes needs the string repr of the
             #    raw name index for LOAD_GLOBAL, LOAD_CONST, etc.
             argval = arg
-            if deop in hasconst:
+            if deop in hasconst or deop == LOAD_SMALL_INT:
                 argval, argrepr = _get_const_info(deop, arg, self.co_consts)
             elif deop in hasname:
                 if deop == LOAD_GLOBAL:
CPython versions tested on:

3.14

Operating systems tested on:

macOS

Linked PRs
  • gh-140258

Contributor guide

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First steps

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  3. Fork the repository and make your change on a branch.
  4. Open a pull request that references the issue number.

Research direction

Start in Lib/dis.py at the Bytecode argument-handling logic and reproduce the example with list(Bytecode("1")). Check the LOAD_SMALL_INT path and _get_const_info behavior; done means its Instruction has the expected non-empty argrepr, with behavior checked against the linked gh-140258 work.

Written by the indexing model from the issue text.

Assessment

Tech stack
python
Domain
devtools
Issue type
Bug
Difficulty
2/5
Estimated time
1-3 hours
Activity status
Stale
Clarity
Clearly specified
Newbie friendliness
25/100

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