GH-30058: [Python] Add StructType attribute to access all its fields (#…

…43481)

### Rationale for this change
Currently you cannot directly access the names of all the fields within a StructType, and it is not obvious how to access each field either. This change allows people to directly access the fields and their names directly. See #30058.

### What changes are included in this PR?
I added a .names and .fields attribute to StructType. 
.names returns a list of the names of the fields in the StructType, and .fields returns a list of the fields in the StructType.

### Are these changes tested?
Yes. I made two tests to check if the new .names and .fields attributes would operate as intended. The tests check if the .names attribute would return a list of the names of each field and if .fields returns a list of the fields.

### Are there any user-facing changes?
Yes, there are two new attributes users can now use.

* GitHub Issue: #30058

Authored-by: Abhinand-J <wabhinandj@gmail.com>
Signed-off-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>

python/pyarrow/tests/test_types.py

@@ -693,6 +693,8 @@ def test_struct_type():
     assert list(ty) == fields
     assert ty[0].name == 'a'
     assert ty[2].type == pa.int32()
+    assert ty.names == [f.name for f in ty]
+    assert ty.fields == list(ty)
     with pytest.raises(IndexError):
         assert ty[3]
 

python/pyarrow/types.pxi

@@ -1025,6 +1025,33 @@ cdef class StructType(DataType):
     def __reduce__(self):
         return struct, (list(self),)
 
+    @property
+    def names(self):
+        """
+        Lists the field names.
+
+        Examples
+        --------
+        >>> import pyarrow as pa
+        >>> struct_type = pa.struct([('a', pa.int64()), ('b', pa.float64()), ('c', pa.string())])
+        >>> struct_type.names
+        ['a', 'b', 'c']
+        """
+        return [f.name for f in self]
+
+    @property
+    def fields(self):
+        """
+        Lists all fields within the StructType.
+
+        Examples
+        --------
+        >>> import pyarrow as pa
+        >>> struct_type = pa.struct([('a', pa.int64()), ('b', pa.float64()), ('c', pa.string())])
+        >>> struct_type.fields
+        [pyarrow.Field<a: int64>, pyarrow.Field<b: double>, pyarrow.Field<c: string>]
+        """
+        return list(self)
 
 cdef class UnionType(DataType):
     """