apacheGH-42016: [Python] Expose new FLOAT16 logical type in the pyarr…

…ow.parquet bindings (apache#42103)

### Rationale for this change
Resolves apache#42016.

### What changes are included in this PR?
Expose new `FLOAT16` logical type in the `pyarrow.parquet` bindings

### Are these changes tested?
Unit test added.

### Are there any user-facing changes?
No.

* GitHub Issue: apache#42016

Authored-by: Tai Le Manh <manhtai.lmt@gmail.com>
Signed-off-by: Joris Van den Bossche <jorisvandenbossche@gmail.com>

python/pyarrow/_parquet.pxd

@@ -64,6 +64,7 @@ cdef extern from "parquet/api/schema.h" namespace "parquet" nogil:
         ParquetLogicalType_TIME" parquet::LogicalType::Type::TIME"
         ParquetLogicalType_TIMESTAMP" parquet::LogicalType::Type::TIMESTAMP"
         ParquetLogicalType_INT" parquet::LogicalType::Type::INT"
+        ParquetLogicalType_FLOAT16" parquet::LogicalType::Type::FLOAT16"
         ParquetLogicalType_JSON" parquet::LogicalType::Type::JSON"
         ParquetLogicalType_BSON" parquet::LogicalType::Type::BSON"
         ParquetLogicalType_UUID" parquet::LogicalType::Type::UUID"

python/pyarrow/_parquet.pyx

@@ -1299,6 +1299,7 @@ cdef logical_type_name_from_enum(ParquetLogicalTypeId type_):
         ParquetLogicalType_TIME: 'TIME',
         ParquetLogicalType_TIMESTAMP: 'TIMESTAMP',
         ParquetLogicalType_INT: 'INT',
+        ParquetLogicalType_FLOAT16: 'FLOAT16',
         ParquetLogicalType_JSON: 'JSON',
         ParquetLogicalType_BSON: 'BSON',
         ParquetLogicalType_UUID: 'UUID',

python/pyarrow/tests/parquet/common.py

@@ -144,6 +144,7 @@ def alltypes_sample(size=10000, seed=0, categorical=False):
         'int16': np.arange(size, dtype=np.int16),
         'int32': np.arange(size, dtype=np.int32),
         'int64': np.arange(size, dtype=np.int64),
+        'float16': np.arange(size, dtype=np.float16),
         'float32': np.arange(size, dtype=np.float32),
         'float64': np.arange(size, dtype=np.float64),
         'bool': np.random.randn(size) > 0,

python/pyarrow/tests/parquet/test_metadata.py

@@ -81,10 +81,12 @@ def test_parquet_metadata_api():
     assert col.max_definition_level == 1
     assert col.max_repetition_level == 0
     assert col.max_repetition_level == 0
-
     assert col.physical_type == 'BOOLEAN'
     assert col.converted_type == 'NONE'
 
+    col_float16 = schema[5]
+    assert col_float16.logical_type.type == 'FLOAT16'
+
     with pytest.raises(IndexError):
         schema[ncols + 1]  # +1 for index