Why does asarray() create an intermediate memoryview?
In the following session a numpy array is created from an stdlib array: In [1]: import array In [2]: base = array.array('i', [1, 2]) In [3]: a = np.asarray(base) In [4]: a.base Out[4]: <memory at 0x7fb80383e8c8> In [5]: a.base.obj Out[5]: array('i', [1, 2]) In [6]: a.base.obj is base Out[6]: True Why can't a.base be base? What is the need for the intermediate memoryview object?
Sun, 27 Mar 2016 17:00:51 -0400, Alexander Belopolsky kirjoitti: [clip]
Why can't a.base be base? What is the need for the intermediate memoryview object?
Implementation detail vs. life cycle management of buffer acquisitions. The PEP3118 Py_buffer structure representing an acquired buffer is a C struct that is not safe to copy (!), and needs to sit in an allocated blob of memory whose life cycle has to be managed. The acquisition also needs to be released after use. Python's memoryview object happens to be a convenient way to babysit this. Rather than adding a new entry to the ArrayObject struct for a potential acquired buffer and inserting corresponding release calls, I picked a more localized solution where the acquisition is managed by the memoryview object rather than ndarray itself, and the life cycle works out via the pre-existing ndarray.base refcounting. -- Pauli Virtanen
Sun, 27 Mar 2016 17:00:51 -0400, Alexander Belopolsky kirjoitti: [clip]
Why can't a.base be base? What is the need for the intermediate memoryview object?
Implementation detail vs. life cycle management of buffer acquisitions. The PEP3118 Py_buffer structure representing an acquired buffer is a C struct that is not safe to copy (!), and needs to sit in an allocated blob of memory whose life cycle has to be managed. The acquisition also needs to be released after use. Python's memoryview object happens to be a convenient way to babysit this. Rather than adding a new entry to the ArrayObject struct for a potential acquired buffer and inserting corresponding release calls, I picked a more localized solution where the acquisition is managed by the memoryview object rather than ndarray itself, and the life cycle works out via the pre-existing ndarray.base refcounting. -- Pauli Virtanen
participants (2)
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Alexander Belopolsky -
Pauli Virtanen