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import re |
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from langchain_core.output_parsers import BaseOutputParser |
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class BooleanOutputParser(BaseOutputParser[bool]): |
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"""Parse the output of an LLM call to a boolean.""" |
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true_val: str = "YES" |
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"""The string value that should be parsed as True.""" |
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false_val: str = "NO" |
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"""The string value that should be parsed as False.""" |
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def parse(self, text: str) -> bool: |
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"""Parse the output of an LLM call to a boolean. |
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Args: |
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text: output of a language model |
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Returns: |
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boolean |
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""" |
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regexp = rf"\b({self.true_val}|{self.false_val})\b" |
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truthy = { |
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val.upper() |
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for val in re.findall(regexp, text, flags=re.IGNORECASE | re.MULTILINE) |
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} |
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if self.true_val.upper() in truthy: |
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if self.false_val.upper() in truthy: |
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raise ValueError( |
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f"Ambiguous response. Both {self.true_val} and {self.false_val} " |
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f"in received: {text}." |
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) |
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return True |
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elif self.false_val.upper() in truthy: |
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if self.true_val.upper() in truthy: |
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raise ValueError( |
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f"Ambiguous response. Both {self.true_val} and {self.false_val} " |
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f"in received: {text}." |
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) |
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return False |
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raise ValueError( |
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f"BooleanOutputParser expected output value to include either " |
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f"{self.true_val} or {self.false_val}. Received {text}." |
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) |
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@property |
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def _type(self) -> str: |
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"""Snake-case string identifier for an output parser type.""" |
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return "boolean_output_parser" |
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