René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Regression on inplace arithmetic operators for numpy\u003e=2","articleBody":"I noticed a bunch of failing tests in a library I'm maintaining when I moved my CI to numpy 2+.\nI was relying on python-quantities, and I was making use of `__imul__`, `__iadd__`, etc.\n\nI guess I (we) didn't quite get the semantics right for array wrapping for `numpy\u003e=2`.\n\nHere's a reproducer:\n```python\nimport quantities as pq\nvelocity = 3 * pq.m/pq.s\ntime = 2*pq.s\ndistance = velocity.copy()\ndistance *= time  # \u003c--- this is the problematic part, if we write distance = distance * time, things work as expected even using numpy\u003e=2\nn_centimeters = distance.rescale(pq.centimeter)\nprint(n_centimeters)\nn_cm_ul = n_centimeters.magnitude.item()\nassert isinstance(n_cm_ul, float)\nerr = n_cm_ul - 300*2\nprint(f\"{err=}\")\nassert abs(err) \u003c 1e-12\n```\n\nExecuting it with numpy 1.26.4 and numpy 2+:\n```\n(cpython-v3.13-apt-deb) 13:38 root@argus:/home/bjorn/vc/chempy# python regression_quantities2.py \n600.0 cm\nerr=0.0\n(cpython-v3.13-apt-deb) 13:38 root@argus:/home/bjorn/vc/chempy# pip install 'numpy\u003e2'\nCollecting numpy\u003e2\n  Downloading numpy-2.3.1-cp313-cp313-manylinux_2_28_x86_64.whl.metadata (62 kB)\nDownloading numpy-2.3.1-cp313-cp313-manylinux_2_28_x86_64.whl (16.6 MB)\n   ━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━━ 16.6/16.6 MB 48.0 MB/s eta 0:00:00\nInstalling collected packages: numpy\n  Attempting uninstall: numpy\n    Found existing installation: numpy 1.26.4\n    Uninstalling numpy-1.26.4:\n      Successfully uninstalled numpy-1.26.4\nSuccessfully installed numpy-2.3.1\n(cpython-v3.13-apt-deb) 13:38 root@argus:/home/bjorn/vc/chempy# python regression_quantities2.py \nTraceback (most recent call last):\n  File \"/opt-3/cpython-v3.13-apt-deb/lib/python3.13/site-packages/quantities/quantity.py\", line 216, in rescale\n    cf = get_conversion_factor(from_u, to_u)\n  File \"/opt-3/cpython-v3.13-apt-deb/lib/python3.13/site-packages/quantities/quantity.py\", line 52, in get_conversion_factor\n    assert from_u.dimensionality == to_u.dimensionality\n           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^\nAssertionError\n\nDuring handling of the above exception, another exception occurred:\n\nTraceback (most recent call last):\n  File \"/home/bjorn/vc/chempy/regression_quantities2.py\", line 6, in \u003cmodule\u003e\n    n_centimeters = distance.rescale(pq.centimeter)\n  File \"/opt-3/cpython-v3.13-apt-deb/lib/python3.13/site-packages/quantities/quantity.py\", line 218, in rescale\n    raise ValueError(\n    ...\u003c2 lines\u003e...\n    )\nValueError: Unable to convert between units of \"m/s\" and \"cm\"\n```\n\nAs a work around, I have changed all my call sites from expressions of the form:\n```python\nmy_dict[key] *= other\n```\nto:\n```python\nmy_dict[key] = my_dict[key] * other   # \u003c--- works with current released quantities \u0026 numpy\u003e=2\n```","author":{"url":"https://github.com/bjodah","@type":"Person","name":"bjodah"},"datePublished":"2025-06-22T11:44:11.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":2},"url":"https://github.com/258/python-quantities/issues/258"}