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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Bug: unclear handling of arrays of different shape with to_arrays","articleBody":"## Bug Report\n\n### Description\nto_arrays() cannot combine arrays of different shape if they differ on 2. axis, but can handle different size arrays when they differ on 1. axis.\n \n### Reproducibility\n```\nimport numpy as np\nimport datajoint as dj\n\ndj.conn()  # using datajoint.json\nschema = dj.Schema(\"TEST\")\n\n\n@schema\nclass RandomNumbers(dj.Manual):\n    definition = \"\"\"\n    idx: int32\n    ---\n    values1: \u003cblob\u003e\n    values2: \u003cblob\u003e\n    \"\"\"\nfor idx,seed in enumerate([42, 7, 123]):\n    RandomNumbers.insert1(\n        {\n            \"idx\": idx,\n            \"values1\": np.random.RandomState(seed).randn(100) if idx==0 else np.random.RandomState(seed).randn(100,idx),            \n            \"values2\": np.random.RandomState(seed).randn(100) if idx==0 else np.random.RandomState(seed).randn(idx,100),\n        }\n    )\n```\n\n```\nRandomNumbers.to_arrays('values2').shape  # returns 3\n```\n```\nRandomNumbers.to_arrays('values1').shape  # fails\n```\n\n```\n---------------------------------------------------------------------------\nValueError                                Traceback (most recent call last)\nFile ~/datajoint-python/src/datajoint/expression.py:859, in QueryExpression.to_arrays(self, include_key, order_by, limit, offset, squeeze, *attrs)\n    858 try:\n--\u003e 859     arr = np.array(values)\n    860 except ValueError:\n    861     # Variable-size data (e.g., arrays of different shapes)\n\nValueError: setting an array element with a sequence. The requested array has an inhomogeneous shape after 2 dimensions. The detected shape was (3, 100) + inhomogeneous part.\n\nDuring handling of the above exception, another exception occurred:\n\nValueError                                Traceback (most recent call last)\nCell In[17], line 1\n----\u003e 1 RandomNumbers.to_arrays('values1')\n\nFile ~/datajoint-python/src/datajoint/expression.py:862, in QueryExpression.to_arrays(self, include_key, order_by, limit, offset, squeeze, *attrs)\n    859         arr = np.array(values)\n    860     except ValueError:\n    861         # Variable-size data (e.g., arrays of different shapes)\n--\u003e 862         arr = np.array(values, dtype=object)\n    863     result_arrays.append(arr)\n    865 if include_key:\n\nValueError: could not broadcast input array from shape (100,1) into shape (100,)\n```\n### Expected Behavior\nIf arrays cannot be broadcast together, they should be stacked  as is done with values2 in the example. \n\n","author":{"url":"https://github.com/arturoptophys","@type":"Person","name":"arturoptophys"},"datePublished":"2026-02-05T13:50:23.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":1},"url":"https://github.com/1380/datajoint-python/issues/1380"}