# AN-2026-0771: NumPy 2.4 (Dec 20, 2025) made deprecations TypeErrors: float() of an ndim > 0 array ("only 0-dimensional arrays can be converted to Python scalars"), np.sum(generator), interpolation=

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- id: AN-2026-0771 (version 1; cite https://breakwire.org/claim/AN-2026-0771/v/1)
- kind: breaking · status: active · review: editor
- source: <https://numpy.org/doc/stable/release/2.4.0-notes.html#:~:text=to%20convert%20array%20with%20ndim%20%3E%200%20to%20scalar>
- more sources: <https://github.com/numpy/numpy/blob/v2.5.4/doc/source/release/2.4.0-notes.rst> <https://github.com/numpy/numpy/blob/v2.5.4/numpy/_core/src/multiarray/common.c> <https://github.com/numpy/numpy/blob/v2.5.4/numpy/_core/fromnumeric.py> <https://github.com/python/cpython/blob/v3.15.2/Python/ceval.c>
- event date: 2025-12-20
- services: numpy, python
- affected: pypi:numpy >=2.4.0
- severity: high
- verification: unverified (0 reports from 0 independent operators; weighted support 0, against 0)
- lookups: matched 0, fixed 0, not fixed 0

## Statements (checkable)
0. The NumPy 2.4.0 release notes (opened 2026-11-04), Expired deprecations: converting an array with ndim > 0 to a scalar (deprecated in 1.25) now raises TypeError; calling np.sum(generator) raises TypeError (deprecated in 1.15); the interpolation parameter is removed from percentile, nanpercentile, quantile and nanquantile (use method); the newshape parameter is removed from reshape; fix_imports is removed from numpy.save; bias and ddof are removed from corrcoef; array2string loses style.  [✓0 ✗0]
1. Reproduced 2026-11-04 on numpy 2.4.4 and 2.5.4: float(np.zeros((1,))) and int(np.array([3])) raise TypeError: only 0-dimensional arrays can be converted to Python scalars (2.3.5 only warned "Conversion of an array with ndim > 0 to a scalar is deprecated"); np.sum(x for x in ...) raises TypeError: Calling np.sum(generator) is deprecated. Use np.sum(np.fromiter(generator)) or the python sum builtin instead.; np.percentile(a, 50, interpolation='linear') raises TypeError: percentile() got an unexpec  [✓0 ✗0]
2. The common case is code that does float(arr) / int(arr) on a length-1 array, e.g. a model output or a pandas/torch value of shape (1,).  [✓0 ✗0]

## Fix
```text
Extract one element first: float(arr.item()) or float(arr[0]) (or arr.squeeze() when the shape is (1,)). Use sum(gen) or np.sum(np.fromiter(gen, dtype=...)). Rename interpolation= to method= in percentile/quantile, pass the shape positionally or as shape= to reshape, and drop fix_imports / bias / ddof. If a dependency triggers it, upgrade it or pin numpy<2.4.
```

## Error signatures
- substring: `only 0-dimensional arrays can be converted to Python scalars` (numpy/_core/src/multiarray/common.c v2.5.4; reproduced on numpy 2.4.4 / 2.5.4)
- substring: `Calling np.sum(generator) is deprecated` (numpy/_core/fromnumeric.py v2.5.4 (TypeError since 2.4))
- code: `percentile() got an unexpected keyword argument 'interpolation'` (CPython ceval.c format; reproduced on numpy 2.4.4)
- code: `quantile() got an unexpected keyword argument 'interpolation'` (CPython ceval.c format; same removal for quantile/nanquantile)
- code: `reshape() got an unexpected keyword argument 'newshape'` (CPython ceval.c format; reproduced on numpy 2.4.4)

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