jorisvandenbossche commented on pull request #8271:
URL: https://github.com/apache/arrow/pull/8271#issuecomment-701380049
> This also raised a question: Should both the list entry and the string
array entry have a missing/null value if the input string contains a null
value? I think it should because if we ask for the underlying string array, and
the string value that the missing list entry points to is not a missing value,
it will be an empty string, which seems odd to me.
Buf if the original string was a null, then the output also contains a
(top-level) null, and not a list with a null?
And then such top-level nulls are typically not put as an entry in the
actual values array (or at least when arrow is building up a list array itself,
the format might also not allow otherwise). Eg:
```
In [10]: arr = pa.array([["a", "b"], None, ["c"], [None]])
In [11]: arr
Out[11]:
<pyarrow.lib.ListArray object at 0x7f2316c1d108>
[
[
"a",
"b"
],
null,
[
"c"
],
[
null
]
]
In [12]: arr.values
Out[12]:
<pyarrow.lib.StringArray object at 0x7f2316c1d5e8>
[
"a",
"b",
"c",
null
]
```
(so only the null that was inside a list is represented as null in the
underlying values array)
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