Allow to_pyarrow_table() to take an optional list of partitions (#221)

This will help ensure that Python is only loading what's necessary

Fixes #220

python/deltalake/table.py

@@ -183,13 +183,23 @@ def pyarrow_schema(self) -> pyarrow.Schema:
         """
         return pyarrow_schema_from_json(self._table.arrow_schema_json())
 
-    def to_pyarrow_dataset(self) -> pyarrow.dataset.Dataset:
+    def to_pyarrow_dataset(
+        self, partitions: Optional[List[Tuple]] = None
+    ) -> pyarrow.dataset.Dataset:
         """
         Build a PyArrow Dataset using data from the DeltaTable.
 
+        :param partitions: A list of partition filters, see help(DeltaTable.files_by_partitions) for filter syntax
         :return: the PyArrow dataset in PyArrow
         """
-        file_paths = self._table.file_paths()
+        if partitions is None:
+            file_paths = self._table.file_paths()
+        else:
+            table_path = self._table.table_path()
+            file_paths = [
+                f"{table_path}/{file_name}"
+                for file_name in self._table.files_by_partitions(partitions)
+            ]
         paths = [urlparse(curr_file) for curr_file in file_paths]
 
         # Decide based on the first file, if the file is on cloud storage or local
@@ -222,10 +232,13 @@ def to_pyarrow_dataset(self) -> pyarrow.dataset.Dataset:
                 partitioning=partitioning(flavor="hive"),
             )
 
-    def to_pyarrow_table(self) -> pyarrow.Table:
+    def to_pyarrow_table(
+        self, partitions: Optional[List[Tuple]] = None
+    ) -> pyarrow.Table:
         """
         Build a PyArrow Table using data from the DeltaTable.
 
+        :param partitions: A list of partition filters, see help(DeltaTable.files_by_partitions) for filter syntax
         :return: the PyArrow table
         """
-        return self.to_pyarrow_dataset().to_table()
+        return self.to_pyarrow_dataset(partitions).to_table()