René's URL Explorer Experiment

{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"Bug: fetch in DJ2.0 behaves differently compared to DJ. 0.14","articleBody":"## Bug Report\n\n### Description\nNow that fetch has returned for backwards compatibility. I see 3 differences which might still lead to issues:\n\n1. fetch seems not to be classmethod anymore\n2. fetch defaults to as_dict=True in dj.2.0 but was as_dict=False in dj.0.14\n3. fetch('KEY') doesnt work  \n\n### Reproducibility\n\n```\nimport numpy as np\nimport datajoint as dj\n\ndj.conn()  # using datajoint.json\nschema = dj.Schema(\"TEST\")\n\n@schema\nclass RandomLookup(dj.Lookup):\n    definition = \"\"\"\n    idx: int32\n    ---\n    values1: float32\n    \"\"\"\n    contents = [(0, 0.0), (1, 1.0), (2, 2.0), (3, 3.0), (4, 4.0)]\n```\n\n1. \n`\nRandomLookup.fetch('values1')  # works in dj.014\n `\n```\n---------------------------------------------------------------------------\nAttributeError                            Traceback (most recent call last)\nCell In[38], line 1\n----\u003e 1 RandomLookup.fetch('values1')\n\nFile ~/datajoint-python/src/datajoint/expression.py:654, in QueryExpression.fetch(self, offset, limit, order_by, format, as_dict, squeeze, *attrs)\n    651     return self.to_dicts(order_by=order_by, limit=limit, offset=offset, squeeze=squeeze)\n    653 # Default: return structured array (legacy behavior)\n--\u003e 654 return self.to_arrays(order_by=order_by, limit=limit, offset=offset, squeeze=squeeze)\n\nAttributeError: 'str' object has no attribute 'to_arrays'\n```\n2.\n`\nprint(isinstance(RandomLookup().fetch('values1')[0],dict)) # True  \n`\n\n`\nprint(isinstance(RandomLookup().fetch('values1',as_dict=False)[0],dict)) # False \n`\n\n3.\n\n`RandomNumbers().fetch('KEY')`\n\n```\n---------------------------------------------------------------------------\nDataJointError                            Traceback (most recent call last)\nCell In[41], line 1\n----\u003e 1 RandomNumbers().fetch('KEY')\n\nFile ~/datajoint-python/src/datajoint/expression.py:644, in QueryExpression.fetch(self, offset, limit, order_by, format, as_dict, squeeze, *attrs)\n    641 if attrs:\n    642     if as_dict or as_dict is None:\n    643         # fetch('col1', 'col2', as_dict=True) or fetch('col1', 'col2')\n--\u003e 644         return self.proj(*attrs).to_dicts(order_by=order_by, limit=limit, offset=offset, squeeze=squeeze)\n    645     else:\n    646         # fetch('col1', 'col2', as_dict=False) -\u003e tuple of arrays\n    647         return self.to_arrays(*attrs, order_by=order_by, limit=limit, offset=offset, squeeze=squeeze)\n\nFile ~/datajoint-python/src/datajoint/expression.py:498, in QueryExpression.proj(self, *attributes, **named_attributes)\n    496 # check that all attributes exist in heading\n    497 try:\n--\u003e 498     raise DataJointError(\"Attribute `%s` not found.\" % next(a for a in attributes if a not in self.heading.names))\n    499 except StopIteration:\n    500     pass  # all ok\n\nDataJointError: Attribute `KEY` not found.\n```","author":{"url":"https://github.com/arturoptophys","@type":"Person","name":"arturoptophys"},"datePublished":"2026-02-05T14:07:48.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":3},"url":"https://github.com/1381/datajoint-python/issues/1381"}