_transform() — langchain Function Reference

Architecture documentation for the _transform() function in transform.py from the langchain codebase.

Function python OutputParsing StreamingParsers calls 2 called by 1

Entity Profile

OutputParsing→ StreamingParsers→ _transform() — langchain Function Reference

Dependency Diagram

graph TD
  e9d78389_411d_b432_b3e7_9127c9ec4ca8["_transform()"]
  824fa229_797b_3ac5_af95_3865f109a642["BaseCumulativeTransformOutputParser"]
  e9d78389_411d_b432_b3e7_9127c9ec4ca8 -->|defined in| 824fa229_797b_3ac5_af95_3865f109a642
  1f74e811_a1f8_f140_111a_7e0ac22ffb35["_transform()"]
  1f74e811_a1f8_f140_111a_7e0ac22ffb35 -->|calls| e9d78389_411d_b432_b3e7_9127c9ec4ca8
  8382e624_b7a0_ea89_30ff_da6c3c317638["_diff()"]
  e9d78389_411d_b432_b3e7_9127c9ec4ca8 -->|calls| 8382e624_b7a0_ea89_30ff_da6c3c317638
  1f74e811_a1f8_f140_111a_7e0ac22ffb35["_transform()"]
  e9d78389_411d_b432_b3e7_9127c9ec4ca8 -->|calls| 1f74e811_a1f8_f140_111a_7e0ac22ffb35
  style e9d78389_411d_b432_b3e7_9127c9ec4ca8 fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/core/langchain_core/output_parsers/transform.py lines 126–148

    def _transform(self, input: Iterator[str | BaseMessage]) -> Iterator[Any]:
        prev_parsed = None
        acc_gen: GenerationChunk | ChatGenerationChunk | None = None
        for chunk in input:
            chunk_gen: GenerationChunk | ChatGenerationChunk
            if isinstance(chunk, BaseMessageChunk):
                chunk_gen = ChatGenerationChunk(message=chunk)
            elif isinstance(chunk, BaseMessage):
                chunk_gen = ChatGenerationChunk(
                    message=BaseMessageChunk(**chunk.model_dump())
                )
            else:
                chunk_gen = GenerationChunk(text=chunk)

            acc_gen = chunk_gen if acc_gen is None else acc_gen + chunk_gen  # type: ignore[operator]

            parsed = self.parse_result([acc_gen], partial=True)
            if parsed is not None and parsed != prev_parsed:
                if self.diff:
                    yield self._diff(prev_parsed, parsed)
                else:
                    yield parsed
                prev_parsed = parsed