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docs/reference: Mention that slicing a memoryview causes allocation.

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This commit is contained in:
Peter Hinch
2021-08-27 17:45:13 +01:00
committed by Damien George
parent 4954290e86
commit 3720a570f2
1 changed files with 5 additions and 3 deletions
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docs/reference/speed_python.rst
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@@ -91,9 +91,11 @@ code these should be pre-allocated and passed as arguments or as bound objects.
When passing slices of objects such as `bytearray` instances, Python creates When passing slices of objects such as `bytearray` instances, Python creates
a copy which involves allocation of the size proportional to the size of slice. a copy which involves allocation of the size proportional to the size of slice.
This can be alleviated using a `memoryview` object. `memoryview` itself This can be alleviated using a `memoryview` object. The `memoryview` itself
is allocated on heap, but is a small, fixed-size object, regardless of the size is allocated on the heap, but is a small, fixed-size object, regardless of the size
of slice it points too. of slice it points too. Slicing a `memoryview` creates a new `memoryview`, so this
cannot be done in an interrupt service routine. Further, the slice syntax ``a:b``
causes further allocation by instantiating a ``slice(a, b)`` object.
.. code:: python .. code:: python