feat: Add set node account id method

CHANGELOG.md

@@ -21,6 +21,8 @@ This changelog is based on [Keep a Changelog](https://keepachangelog.com/en/1.1.
 - Added expiration_time, auto_renew_period, auto_renew_account, fee_schedule_key, kyc_key in `TokenCreateTransaction`, `TokenUpdateTransaction` classes
 - Added comprehensive Google-style docstrings to the `CustomFee` class and its methods in `custom_fee.py`.
 - docs: Add `docs/sdk_developers/project_structure.md` to explain repository layout and import paths.
+- Support selecting specific node account ID(s) for queries and transactions (#362)
+- Added `Network._get_node()` method and updated execution flow to use node selection (#362)
 
 ### Changed
 - chore: validate that token airdrop transactions require an available token service on the channel (#632) 

src/hiero_sdk_python/client/network.py

@@ -171,6 +171,21 @@ def _select_node(self) -> _Node:
         self._node_index = (self._node_index + 1) % len(self.nodes)
         self.current_node = self.nodes[self._node_index]
         return self.current_node
+
+    def _get_node(self, account_id: AccountId) -> Optional[_Node]:
+        """
+        Get a node matching the given account ID.
+
+        Args:
+            account_id (AccountId): The account ID of the node to locate.
+
+        Returns:
+            Optional[_Node]: The matching node, or None if not found.
+        """
+        for node in self.nodes:
+            if node._account_id == account_id:
+                return node
+        return None
 
     def get_mirror_address(self) -> str:
         """

src/hiero_sdk_python/executable.py

@@ -176,10 +176,15 @@ def _execute(self, client: "Client"):
             if attempt > 0 and current_backoff < self._max_backoff:
                 current_backoff *= 2
 
-            # Set the node account id to the client's node account id
-            node = client.network.current_node
-            self.node_account_id = node._account_id
-
+            # Select preferred node if provided, fallback to client's default
+            selected_node_account_id = (
+                self._select_node_account_id()
+                or client.network.current_node._account_id
+            )
+
+            self.node_account_id = selected_node_account_id
+            node = client.network._get_node(self.node_account_id)
+
             # Create a channel wrapper from the client's channel
             channel = node._get_channel()
 

src/hiero_sdk_python/query/query.py

@@ -59,6 +59,9 @@ def __init__(self) -> None:
         self.node_index: int = 0
         self.payment_amount: Optional[Hbar] = None
 
+        self.node_account_ids: Optional[List[AccountId]] = None
+        self._used_node_account_id: Optional[AccountId] = None
+
     def _get_query_response(self, response: Any) -> query_pb2.Query:
         """
         Extracts the query-specific response object from the full response.
@@ -379,3 +382,44 @@ def _is_payment_required(self) -> bool:
             bool: True if payment is required, False otherwise
         """
         return True
+
+    def set_node_account_ids(self, node_account_ids: List[AccountId]): 
+        """
+        Sets the list of node account IDs the query can be sent to.
+
+        Args:
+            node_account_ids (List[AccountId]): The list of node account IDs.
+
+        Returns:
+            Self: Returns self for method chaining.
+        """
+        self.node_account_ids = node_account_ids
+        return self
+
+    def set_node_account_id(self, node_account_id: AccountId):
+        """
+        Sets a single node account ID the query will be sent to.
+
+        Args:
+            node_account_id (AccountId): The node account ID.
+
+        Returns:
+            Self: Returns self for method chaining.
+        """
+
+        return self.set_node_account_ids([node_account_id])
+
+    def _select_node_account_id(self) -> Optional[AccountId]:
+        """
+        Internal method to select a node account ID to send the query to.
+        Defaults to the first in the list.
+
+        Returns:
+            Optional[AccountId]: The selected node account ID.
+        """
+        if self.node_account_ids:
+            selected = self.node_account_ids[0]
+            self._used_node_account_id = selected 
+            return selected 
+        return None
+

src/hiero_sdk_python/transaction/transaction.py

@@ -1,5 +1,5 @@
 import hashlib
-from typing import Optional
+from typing import List, Optional
 
 from typing import TYPE_CHECKING
 
@@ -59,7 +59,10 @@ def __init__(self) -> None:
         # and ensures that the correct signatures are used when submitting transactions
         self._signature_map: dict[bytes, basic_types_pb2.SignatureMap] = {}
         self._default_transaction_fee = 2_000_000
-        self.operator_account_id = None  
+        self.operator_account_id = None
+
+        self.node_account_ids: Optional[List[AccountId]] = None
+        self._used_node_account_id: Optional[AccountId] = None
 
     def _make_request(self):
         """

tests/unit/test_query_nodes.py

@@ -0,0 +1,31 @@
+import pytest
+from hiero_sdk_python.query.query import Query
+from hiero_sdk_python.account.account_id import AccountId
+
+def test_set_single_node_account_id():
+    q = Query()
+    node = AccountId(0, 0, 3)
+
+    q.set_node_account_id(node)
+
+    assert q.node_account_ids == [node]
+    assert q._used_node_account_id is None  # not selected until execution
+
+def test_set_multiple_node_account_ids():
+    q = Query()
+    nodes = [AccountId(0, 0, 3), AccountId(0, 0, 4)]
+
+    q.set_node_account_ids(nodes)
+
+    assert q.node_account_ids == nodes
+    assert q._used_node_account_id is None
+
+def test_select_node_account_id():
+    q = Query()
+    nodes = [AccountId(0, 0, 3), AccountId(0, 0, 4)]
+    q.set_node_account_ids(nodes)
+
+    selected = q._select_node_account_id()
+
+    assert selected == nodes[0]
+    assert q._used_node_account_id == nodes[0]

tests/unit/test_transaction_nodes.py

@@ -0,0 +1,52 @@
+import pytest
+from hiero_sdk_python.transaction.transaction import Transaction
+from hiero_sdk_python.account.account_id import AccountId
+
+
+class DummyTransaction(Transaction):
+    """
+    Minimal subclass of Transaction for testing.
+    Transaction is abstract (requires build methods), so we stub them out.
+    """
+    def __init__(self):
+        super().__init__()
+
+    def build_base_transaction_body(self):
+        return None  # stub
+
+    def _make_request(self):
+        return None  # stub
+
+    def _get_method(self):
+        return None  # stub
+
+
+def test_set_single_node_account_id():
+    txn = DummyTransaction()
+    node = AccountId(0, 0, 3)
+
+    txn.set_node_account_id(node)
+
+    assert txn.node_account_ids == [node]
+    assert txn._used_node_account_id is None
+
+
+def test_set_multiple_node_account_ids():
+    txn = DummyTransaction()
+    nodes = [AccountId(0, 0, 3), AccountId(0, 0, 4)]
+
+    txn.set_node_account_ids(nodes)
+
+    assert txn.node_account_ids == nodes
+    assert txn._used_node_account_id is None
+
+
+def test_select_node_account_id():
+    txn = DummyTransaction()
+    nodes = [AccountId(0, 0, 3), AccountId(0, 0, 4)]
+    txn.set_node_account_ids(nodes)
+
+    selected = txn._select_node_account_id()
+
+    assert selected == nodes[0]
+    assert txn._used_node_account_id == nodes[0]