# AN-2026-0755: Python 3.14 removed ast.Num, ast.Str, ast.Bytes, ast.NameConstant, ast.Ellipsis and Constant.n / Constant.s: "module 'ast' has no attribute 'Num'"

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- id: AN-2026-0755 (version 1; cite https://breakwire.org/claim/AN-2026-0755/v/1)
- kind: breaking · status: active · review: editor
- source: <https://docs.python.org/3/whatsnew/3.14.html#:~:text=Remove%20the%20following%20classes%2C%20which%20have%20been%20deprecated%20aliases%20of>
- more sources: <https://github.com/python/cpython/blob/v3.15.2/Objects/moduleobject.c> <https://github.com/python/cpython/blob/v3.15.2/Objects/object.c>
- event date: 2025-10-07
- services: python
- affected: engines.python >=3.14
- severity: medium
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. What's New in Python 3.14 (opened 2026-11-04) says the deprecated ast.Constant aliases Bytes, Ellipsis, NameConstant, Num and Str were removed; visit_Num, visit_Str, visit_Bytes, visit_NameConstant and visit_Ellipsis methods on NodeVisitor subclasses are no longer called (define visit_Constant); and the compatibility properties Constant.n and Constant.s were removed (use Constant.value).  [✓0 ✗0]
1. Reproduced 2026-11-04 on CPython 3.14.10: ast.Num raises AttributeError: module 'ast' has no attribute 'Num'; ast.Constant(1).n raises AttributeError: 'Constant' object has no attribute 'n'. A silent variant: old visit_Str/visit_Num visitors simply stop firing.  [✓0 ✗0]

## Fix
```text
Use ast.Constant and check the type of node.value (isinstance(node, ast.Constant) and isinstance(node.value, str) instead of ast.Str); read node.value instead of node.n / node.s; rename visit_Num/visit_Str/... to a single visit_Constant. Upgrade linters, code generators and template engines that still use the old names.
```

## Error signatures
- code: `module 'ast' has no attribute 'Num'` (CPython message, reproduced 2026-11-04 on CPython 3.14.10)
- code: `module 'ast' has no attribute 'Str'` (CPython message, reproduced 2026-11-04 on CPython 3.14.10)
- code: `module 'ast' has no attribute 'Bytes'` (CPython message, reproduced 2026-11-04 on CPython 3.14.10)
- code: `module 'ast' has no attribute 'NameConstant'` (CPython message, reproduced 2026-11-04 on CPython 3.14.10)
- code: `'Constant' object has no attribute 'n'` (CPython message, reproduced 2026-11-04 on CPython 3.14.10)
- code: `'Constant' object has no attribute 's'` (CPython message, reproduced 2026-11-04 on CPython 3.14.10)

## Outcome reports (0)
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## History
- v1 2026-11-04 by wire-editor: filed from primary source opened 2026-10-28