ianmcook opened a new issue, #41684:
URL: https://github.com/apache/arrow/issues/41684
### Describe the bug, including details regarding any error messages,
version, and platform.
I have a MapArray created like this:
```py
table = pa.table(
{"m": [{"a": 1}, {}, None, {"b": None}]},
schema=pa.schema([pa.field("m", pa.map_(pa.string(), pa.int64()), True)])
)
m = table["m"].chunks[0]
```
Notice that the value at position 2 is null:
```py
m.to_pandas()
## 0 [(a, 1.0)]
## 1 []
## 2 None
## 3 [(b, None)]
## dtype: object
m.is_null()
## <pyarrow.lib.BooleanArray object at 0x1637cb220>
## [
## false,
## false,
## true,
## false
## ]
```
I am trying to reconstruct the MapArray from its constituent arrays, but
when I do this, it always loses the null:
```py
new = pa.MapArray.from_arrays(m.offsets, m.keys, m.items, m.type)
new.to_pandas()
## 0 [(a, 1.0)]
## 1 []
## 2 []
## 3 [(b, None)]
## dtype: object
new.is_null()
## <pyarrow.lib.BooleanArray object at 0x1637cb220>
## [
## false,
## false,
## false,
## false
## ]
```
Wrapping `pa.array(..., mask=m.is_null())` around it does not help either.
Is there any way to reconstruct the MapArray and keep the null?
### Component(s)
Python
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