_on_chain_start() — langchain Function Reference

Architecture documentation for the _on_chain_start() function in stdout.py from the langchain codebase.

Function python Observability Tracers calls 2

Entity Profile

Observability→ Tracers→ _on_chain_start() — langchain Function Reference

Dependency Diagram

graph TD
  42164529_c052_e374_4090_851b8fe251db["_on_chain_start()"]
  56d9fac7_db71_9c71_7cac_1d680d392fa0["FunctionCallbackHandler"]
  42164529_c052_e374_4090_851b8fe251db -->|defined in| 56d9fac7_db71_9c71_7cac_1d680d392fa0
  1bda6774_d332_dec5_ed8f_8d6eef57961e["get_breadcrumbs()"]
  42164529_c052_e374_4090_851b8fe251db -->|calls| 1bda6774_d332_dec5_ed8f_8d6eef57961e
  95875f96_0c2d_b364_e63a_651f8ed4cdcd["try_json_stringify()"]
  42164529_c052_e374_4090_851b8fe251db -->|calls| 95875f96_0c2d_b364_e63a_651f8ed4cdcd
  style 42164529_c052_e374_4090_851b8fe251db fill:#6366f1,stroke:#818cf8,color:#fff

Relationship Graph

Source Code

libs/core/langchain_core/tracers/stdout.py lines 105–112

    def _on_chain_start(self, run: Run) -> None:
        crumbs = self.get_breadcrumbs(run)
        run_type = run.run_type.capitalize()
        self.function_callback(
            f"{get_colored_text('[chain/start]', color='green')} "
            + get_bolded_text(f"[{crumbs}] Entering {run_type} run with input:\n")
            + f"{try_json_stringify(run.inputs, '[inputs]')}"
        )