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{"@context":"https://schema.org","@type":"DiscussionForumPosting","headline":"SharedMemory.unlink() can fail if called during interpreter shutdown","articleBody":"`SharedMemory.unlink()` contains a `import` which can fail if called during interpreter shutdown.\r\n\r\nFor example when working with SharedMemory as the buffer for a numpy array it is useful to create a wrapper object to ensure that clean up is done with the object is deleted. \r\n\r\n```python\r\n#import numpy as np\r\nfrom multiprocessing import shared_memory\r\n\r\nclass ShArray:\r\n    def __init__(self):\r\n        self.shared_memory = shared_memory.SharedMemory(create=True, size=400)\r\n        #self.array = np.ndarray((10,10), dtype=\"i4\", buffer=self.shared_memory.buf)\r\n\r\n    def __del__(self):\r\n        self.shared_memory.close()\r\n        self.shared_memory.unlink()\r\n\r\na1 = ShArray()\r\n```\r\n(Commented lines show my typical usage, but are not need to demonstrate the issue)\r\n\r\n```\r\nException ignored in: \u003cfunction ShArray.__del__ at 0x7f36eee510d0\u003e\r\nTraceback (most recent call last):\r\n  File \"/home/sam/git/cpython/test_shared_mem2.py\", line 13, in __del__\r\n  File \"/home/sam/git/cpython/Lib/multiprocessing/shared_memory.py\", line 240, in unlink\r\nImportError: sys.meta_path is None, Python is likely shutting down\r\n/home/sam/git/cpython/Lib/multiprocessing/resource_tracker.py:224: UserWarning: resource_tracker: There appear to be 1 leaked shared_memory objects to clean up at shutdown\r\n  warnings.warn('resource_tracker: There appear to be %d '\r\n\r\n```\r\nThis happens on 3.8 and current main, both on Linux x86-64.\r\n\r\nPatch to follow","author":{"url":"https://github.com/samtygier","@type":"Person","name":"samtygier"},"datePublished":"2022-04-15T16:13:33.000Z","interactionStatistic":{"@type":"InteractionCounter","interactionType":"https://schema.org/CommentAction","userInteractionCount":4},"url":"https://github.com/91577/cpython/issues/91577"}