[GitHub] [arrow] milesgranger commented on a diff in pull request #13989: ARROW-14495: [Python] Fix DictionaryArray.from_buffers, should not crash

[GitBox <gi...@apache.org>]

milesgranger commented on code in PR #13989:
URL: https://github.com/apache/arrow/pull/13989#discussion_r957138437


##########
python/pyarrow/array.pxi:
##########
@@ -2478,6 +2478,53 @@ cdef class DictionaryArray(Array):
 
         return self._indices
 
+    @staticmethod
+    def from_buffers(DataType type, int64_t length, buffers, Array dictionary,
+                     int64_t null_count=-1, int64_t offset=0):
+        """
+        Construct a DictionaryArray from buffers.
+
+        Parameters
+        ----------
+        type : pyarrow.DataType
+        length : int
+            The number of values in the array.
+        buffers : List[Buffer]
+            The buffers backing this array.
+        dictionary : pyarrow.Array, ndarray or pandas.Series
+            The array of values referenced by the indices.
+        null_count : int, default -1
+            The number of null entries in the array. Negative value means that
+            the null count is not known.
+        offset : int, default 0
+            The array's logical offset (in values, not in bytes) from the
+            start of each buffer.
+
+        Returns
+        -------
+        dict_array : DictionaryArray
+        """
+        cdef:
+            vector[shared_ptr[CBuffer]] c_buffers
+            shared_ptr[CDataType] c_type
+            shared_ptr[CArrayData] c_data
+            shared_ptr[CArray] c_result
+
+        for buf in buffers:
+            c_buffers.push_back(pyarrow_unwrap_buffer(buf))
+
+        c_type = pyarrow_unwrap_data_type(type)
+
+        with nogil:
+            c_data = CArrayData.Make(
+                c_type, length, c_buffers, null_count, offset)
+            c_data.get().dictionary = dictionary.sp_array.get().data()

Review Comment:
   I saw that, and it appears to essentially do the same; creating `ArrayData` then setting the dictionary member. Using it this way, we don't need to pass (null?) child data, albeit, if that way is the preferred method I have no problem switching. 👍 



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