[FEA] Python bindings for column_view::child

[firestarman]

cpp has already supported extracting child columns by index for a column of nested type. It will be much helpful to plumb through to Python.

What's more, it exists in JNI already.

I'm not sure what the Python API should look like. For example we could have:

s = cudf.Series([{"a": 1, "b": "s1"}, {"a": 2, "b": "s2"}])
s.struct.a  # returns Series([1, 2])
s.struct.b  # returns Series(["s1", "s2"])

or alternatively:

s.struct[0]  # returns Series([1, 2])
s.struct[1]  # returns Series(["s1", "s2"])

[kkraus14]

PyArrow does this via a field operator that can take in either a name of the column or the position, where I think it would make sense for us to follow:

s = cudf.Series([{"a": 1, "b": "s1"}, {"a": 2, "b": "s2"}])

s.struct.field('a') # returns Series([1, 2])
s.struct.field(0) # returns Series([1, 2])

s.struct.field('b') # returns Series(["s1", "s2"])
s.struct.field(1) # returns Series(["s1", "s2"])

[skirui-source]

Not sure why this issue is still open? @kkraus14

[kkraus14]

Not sure why this issue is still open? @kkraus14

Not sure, closing, thanks @skirui-source!