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113 lines
3.8 KiB
Python
113 lines
3.8 KiB
Python
"""
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Module for implementing the conditional node
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"""
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from typing import List, Optional
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from simpleeval import EvalWithCompoundTypes, simple_eval
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from .base_node import BaseNode
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class ConditionalNode(BaseNode):
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"""
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A node that determines the next step in the graph's execution flow based on
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the presence and content of a specified key in the graph's state. It extends
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the BaseNode by adding condition-based logic to the execution process.
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This node type is used to implement branching logic within the graph, allowing
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for dynamic paths based on the data available in the current state.
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It is expected that exactly two edges are created out of this node.
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The first node is chosen for execution if the key exists and has a non-empty value,
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and the second node is chosen if the key does not exist or is empty.
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Attributes:
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key_name (str): The name of the key in the state to check for its presence.
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Args:
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key_name (str): The name of the key to check in the graph's state. This is
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used to determine the path the graph's execution should take.
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node_name (str, optional): The unique identifier name for the node. Defaults
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to "ConditionalNode".
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"""
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def __init__(
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self,
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input: str,
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output: List[str],
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node_config: Optional[dict] = None,
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node_name: str = "Cond",
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):
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"""
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Initializes an empty ConditionalNode.
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"""
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super().__init__(node_name, "conditional_node", input, output, 2, node_config)
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try:
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self.key_name = self.node_config["key_name"]
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except (KeyError, TypeError) as e:
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raise NotImplementedError(
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"You need to provide key_name inside the node config"
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) from e
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self.true_node_name = None
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self.false_node_name = None
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self.condition = self.node_config.get("condition", None)
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self.eval_instance = EvalWithCompoundTypes()
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self.eval_instance.functions = {"len": len}
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def execute(self, state: dict) -> dict:
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"""
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Checks if the specified key is present in the state and decides the next node accordingly.
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Args:
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state (dict): The current state of the graph.
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Returns:
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str: The name of the next node to execute based on the presence of the key.
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"""
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if self.true_node_name is None:
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raise ValueError("ConditionalNode's next nodes are not set properly.")
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if self.condition:
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condition_result = self._evaluate_condition(state, self.condition)
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else:
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value = state.get(self.key_name)
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condition_result = value is not None and value != ""
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if condition_result:
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return self.true_node_name
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else:
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return self.false_node_name
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def _evaluate_condition(self, state: dict, condition: str) -> bool:
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"""
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Parses and evaluates the condition expression against the state.
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Args:
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state (dict): The current state of the graph.
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condition (str): The condition expression to evaluate.
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Returns:
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bool: The result of the condition evaluation.
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"""
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# Combine state and allowed functions for evaluation context
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eval_globals = self.eval_instance.functions.copy()
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eval_globals.update(state)
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try:
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result = simple_eval(
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condition,
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names=eval_globals,
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functions=self.eval_instance.functions,
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operators=self.eval_instance.operators,
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)
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return bool(result)
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except Exception as e:
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raise ValueError(
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f"Error evaluating condition '{condition}' in {self.node_name}: {e}"
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)
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