[Python] Provide access to buffers underlying scalars

[asfimport]

I'm building a process to take data from pyarrow Tables and write their data a memory mapped file in a custom format.  Currently, I iterate through the arrow table and must call as_py() only to convert the python value to bytes and write to the memory mapped file.  If the pyarrow scalar API provided a view over the underlying storage, I could simply memcopy the values from the arrow buffer into the mmap buffer.

Reporter: Kyle Kavanagh / @kdkavanagh

_{Note: This issue was originally created as ARROW-16020. Please see the migration documentation for further details.}

[asfimport]

Antoine Pitrou / @pitrou:
In any case, if you iterate in values in Python one by one, it is going to be slow.... Is your custom format not Arrow-compatible?

[asfimport]

Kyle Kavanagh / @kdkavanagh:
Unfortunately not compatible.  The row-wise iteration is exactly what I'm going for: Converting a columnar arrow dataset to a "row-wise" array of C-structs of a similar schema

[github-actions]

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