update how to read from json serialization file

src/pydase/data_service/data_service.py

@@ -17,7 +17,7 @@ from pydase.utils.helpers import (
     generate_paths_from_DataService_dict,
     get_class_and_instance_attributes,
     get_component_class_names,
-    get_nested_value_by_path_and_key,
+    get_nested_value_from_DataService_by_path_and_key,
     get_object_attr_from_path,
     parse_list_attr_and_index,
     update_value_if_changed,
@@ -133,17 +133,21 @@ class DataService(rpyc.Service, AbstractDataService):
         # Traverse the serialized representation and set the attributes of the class
         serialized_class = self.serialize()
         for path in generate_paths_from_DataService_dict(json_dict):
-            value = get_nested_value_by_path_and_key(json_dict, path=path)
+            value = get_nested_value_from_DataService_by_path_and_key(
-            value_type = get_nested_value_by_path_and_key(
+                json_dict, path=path
+            )
+            value_type = get_nested_value_from_DataService_by_path_and_key(
                 json_dict, path=path, key="type"
             )
-            class_value_type = get_nested_value_by_path_and_key(
+            class_value_type = get_nested_value_from_DataService_by_path_and_key(
                 serialized_class, path=path, key="type"
             )
             if class_value_type == value_type:
-                class_attr_is_read_only = get_nested_value_by_path_and_key(
+                class_attr_is_read_only = (
+                    get_nested_value_from_DataService_by_path_and_key(
                         serialized_class, path=path, key="readonly"
                     )
+                )
                 if class_attr_is_read_only:
                     logger.debug(
                         f'Attribute "{path}" is read-only. Ignoring value from JSON '

src/pydase/utils/helpers.py

@@ -1,6 +1,6 @@
 import re
 from itertools import chain
-from typing import Any, Optional
+from typing import Any, Optional, cast
 
 from loguru import logger
 
@@ -126,7 +126,86 @@ def generate_paths_from_DataService_dict(
     return paths
 
 
-def get_nested_value_by_path_and_key(data: dict, path: str, key: str = "value") -> Any:
+def extract_dict_or_list_entry(data: dict[str, Any], key: str) -> dict[str, Any] | None:
+    """
+    Extract a nested dictionary or list entry based on the provided key.
+
+    Given a dictionary and a key, this function retrieves the corresponding nested
+    dictionary or list entry. If the key includes an index in the format "[<index>]",
+    the function assumes that the corresponding entry in the dictionary is a list, and
+    it will attempt to retrieve the indexed item from that list.
+
+    Args:
+        data (dict): The input dictionary containing nested dictionaries or lists.
+        key (str): The key specifying the desired entry within the dictionary. The key
+            can be a regular dictionary key or can include an index in the format
+            "[<index>]" to retrieve an item from a nested list.
+
+    Returns:
+        dict | None: The nested dictionary or list item found for the given key. If the
+            key is invalid, or if the specified index is out of bounds for a list, it
+            returns None.
+
+    Example:
+        >>> data = {
+        ...     "attr1": [
+        ...         {"type": "int", "value": 10}, {"type": "string", "value": "hello"}
+        ...     ],
+        ...     "attr2": {
+        ...         "type": "MyClass",
+        ...         "value": {"sub_attr": {"type": "float", "value": 20.5}}
+        ...     }
+        ... }
+
+        >>> extract_dict_or_list_entry(data, "attr1[1]")
+        {"type": "string", "value": "hello"}
+
+        >>> extract_dict_or_list_entry(data, "attr2")
+        {"type": "MyClass", "value": {"sub_attr": {"type": "float", "value": 20.5}}}
+    """
+
+    attr_name = key
+    index: Optional[int] = None
+
+    # Check if the key contains an index part like '[<index>]'
+    if "[" in key and key.endswith("]"):
+        attr_name, index_part = key.split("[", 1)
+        index_part = index_part.rstrip("]")  # remove the closing bracket
+
+        # Convert the index part to an integer
+        if index_part.isdigit():
+            index = int(index_part)
+        else:
+            logger.error(f"Invalid index format in key: {key}")
+
+    current_data: dict[str, Any] | list[dict[str, Any]] | None = data.get(
+        attr_name, None
+    )
+    if not isinstance(current_data, dict):
+        # key does not exist in dictionary, e.g. when class does not have this
+        # attribute
+        return None
+
+    if isinstance(current_data["value"], list):
+        current_data = current_data["value"]
+
+        if index is not None and 0 <= index < len(current_data):
+            current_data = current_data[index]
+        else:
+            return None
+
+    # When the attribute is a class instance, the attributes are nested in the
+    # "value" key
+    if current_data["type"] not in STANDARD_TYPES:
+        current_data = cast(dict[str, Any], current_data.get("value", None))
+        assert isinstance(current_data, dict)
+
+    return current_data
+
+
+def get_nested_value_from_DataService_by_path_and_key(
+    data: dict[str, Any], path: str, key: str = "value"
+) -> Any:
     """
     Get the value associated with a specific key from a dictionary given a path.
 
@@ -161,35 +240,26 @@ def get_nested_value_by_path_and_key(data: dict, path: str, key: str = "value")
         >>> }
 
         The function can be used to get the value of 'attr1' as follows:
-        >>> get_value_of_key_from_path(data, "attr1")
+        >>> get_nested_value_by_path_and_key(data, "attr1")
         10
 
         It can also be used to get the value of 'attr3', which is nested within 'attr2',
         as follows:
-        >>> get_value_of_key_from_path(data, "attr2.attr3", "type")
+        >>> get_nested_value_by_path_and_key(data, "attr2.attr3", "type")
         float
     """
 
     # Split the path into parts
-    parts = re.split(r"\.|(?=\[\d+\])", path)  # Split by '.' or '['
+    parts: list[str] = re.split(r"\.", path)  # Split by '.'
+    current_data: dict[str, Any] | None = data
 
-    # Traverse the dictionary according to the path parts
     for part in parts:
-        if part.startswith("["):
+        if current_data is None:
-            # List index
+            return
-            idx = int(part[1:-1])  # Strip the brackets and convert to integer
+        current_data = extract_dict_or_list_entry(current_data, part)
-            data = data[idx]
-        else:
-            # Dictionary key
-            data = data[part]
 
-        # When the attribute is a class instance, the attributes are nested in the
+    if isinstance(current_data, dict):
-        # "value" key
+        return current_data.get(key, None)
-        if data["type"] not in STANDARD_TYPES:
-            data = data["value"]
-
-    # Return the value at the terminal point of the path
-    return data[key]
 
 
 def convert_arguments_to_hinted_types(