Source code for langchain_core.runnables.branch

from typing import (
    Any,
    AsyncIterator,
    Awaitable,
    Callable,
    Iterator,
    List,
    Mapping,
    Optional,
    Sequence,
    Tuple,
    Type,
    Union,
    cast,
)

from langchain_core.load.dump import dumpd
from langchain_core.pydantic_v1 import BaseModel
from langchain_core.runnables.base import (
    Runnable,
    RunnableLike,
    RunnableSerializable,
    coerce_to_runnable,
)
from langchain_core.runnables.config import (
    RunnableConfig,
    ensure_config,
    get_async_callback_manager_for_config,
    get_callback_manager_for_config,
    patch_config,
)
from langchain_core.runnables.utils import (
    ConfigurableFieldSpec,
    Input,
    Output,
    get_unique_config_specs,
)


[docs]class RunnableBranch(RunnableSerializable[Input, Output]): """Runnable that selects which branch to run based on a condition. The Runnable is initialized with a list of (condition, Runnable) pairs and a default branch. When operating on an input, the first condition that evaluates to True is selected, and the corresponding Runnable is run on the input. If no condition evaluates to True, the default branch is run on the input. Examples: .. code-block:: python from langchain_core.runnables import RunnableBranch branch = RunnableBranch( (lambda x: isinstance(x, str), lambda x: x.upper()), (lambda x: isinstance(x, int), lambda x: x + 1), (lambda x: isinstance(x, float), lambda x: x * 2), lambda x: "goodbye", ) branch.invoke("hello") # "HELLO" branch.invoke(None) # "goodbye" """ branches: Sequence[Tuple[Runnable[Input, bool], Runnable[Input, Output]]] default: Runnable[Input, Output] def __init__( self, *branches: Union[ Tuple[ Union[ Runnable[Input, bool], Callable[[Input], bool], Callable[[Input], Awaitable[bool]], ], RunnableLike, ], RunnableLike, # To accommodate the default branch ], ) -> None: """A Runnable that runs one of two branches based on a condition.""" if len(branches) < 2: raise ValueError("RunnableBranch requires at least two branches") default = branches[-1] if not isinstance( default, (Runnable, Callable, Mapping), # type: ignore[arg-type] ): raise TypeError( "RunnableBranch default must be runnable, callable or mapping." ) default_ = cast( Runnable[Input, Output], coerce_to_runnable(cast(RunnableLike, default)) ) _branches = [] for branch in branches[:-1]: if not isinstance(branch, (tuple, list)): # type: ignore[arg-type] raise TypeError( f"RunnableBranch branches must be " f"tuples or lists, not {type(branch)}" ) if not len(branch) == 2: raise ValueError( f"RunnableBranch branches must be " f"tuples or lists of length 2, not {len(branch)}" ) condition, runnable = branch condition = cast(Runnable[Input, bool], coerce_to_runnable(condition)) runnable = coerce_to_runnable(runnable) _branches.append((condition, runnable)) super().__init__(branches=_branches, default=default_) # type: ignore[call-arg] class Config: arbitrary_types_allowed = True
[docs] @classmethod def is_lc_serializable(cls) -> bool: """RunnableBranch is serializable if all its branches are serializable.""" return True
[docs] @classmethod def get_lc_namespace(cls) -> List[str]: """Get the namespace of the langchain object.""" return ["langchain", "schema", "runnable"]
[docs] def get_input_schema( self, config: Optional[RunnableConfig] = None ) -> Type[BaseModel]: runnables = ( [self.default] + [r for _, r in self.branches] + [r for r, _ in self.branches] ) for runnable in runnables: if runnable.get_input_schema(config).schema().get("type") is not None: return runnable.get_input_schema(config) return super().get_input_schema(config)
@property def config_specs(self) -> List[ConfigurableFieldSpec]: from langchain_core.beta.runnables.context import ( CONTEXT_CONFIG_PREFIX, CONTEXT_CONFIG_SUFFIX_SET, ) specs = get_unique_config_specs( spec for step in ( [self.default] + [r for _, r in self.branches] + [r for r, _ in self.branches] ) for spec in step.config_specs ) if any( s.id.startswith(CONTEXT_CONFIG_PREFIX) and s.id.endswith(CONTEXT_CONFIG_SUFFIX_SET) for s in specs ): raise ValueError("RunnableBranch cannot contain context setters.") return specs
[docs] def invoke( self, input: Input, config: Optional[RunnableConfig] = None, **kwargs: Any ) -> Output: """First evaluates the condition, then delegate to true or false branch.""" config = ensure_config(config) callback_manager = get_callback_manager_for_config(config) run_manager = callback_manager.on_chain_start( dumpd(self), input, name=config.get("run_name"), run_id=config.pop("run_id", None), ) try: for idx, branch in enumerate(self.branches): condition, runnable = branch expression_value = condition.invoke( input, config=patch_config( config, callbacks=run_manager.get_child(tag=f"condition:{idx + 1}"), ), ) if expression_value: output = runnable.invoke( input, config=patch_config( config, callbacks=run_manager.get_child(tag=f"branch:{idx + 1}"), ), **kwargs, ) break else: output = self.default.invoke( input, config=patch_config( config, callbacks=run_manager.get_child(tag="branch:default") ), **kwargs, ) except BaseException as e: run_manager.on_chain_error(e) raise run_manager.on_chain_end(dumpd(output)) return output
[docs] async def ainvoke( self, input: Input, config: Optional[RunnableConfig] = None, **kwargs: Any ) -> Output: """Async version of invoke.""" config = ensure_config(config) callback_manager = get_async_callback_manager_for_config(config) run_manager = await callback_manager.on_chain_start( dumpd(self), input, name=config.get("run_name"), run_id=config.pop("run_id", None), ) try: for idx, branch in enumerate(self.branches): condition, runnable = branch expression_value = await condition.ainvoke( input, config=patch_config( config, callbacks=run_manager.get_child(tag=f"condition:{idx + 1}"), ), ) if expression_value: output = await runnable.ainvoke( input, config=patch_config( config, callbacks=run_manager.get_child(tag=f"branch:{idx + 1}"), ), **kwargs, ) break else: output = await self.default.ainvoke( input, config=patch_config( config, callbacks=run_manager.get_child(tag="branch:default") ), **kwargs, ) except BaseException as e: await run_manager.on_chain_error(e) raise await run_manager.on_chain_end(dumpd(output)) return output
[docs] def stream( self, input: Input, config: Optional[RunnableConfig] = None, **kwargs: Optional[Any], ) -> Iterator[Output]: """First evaluates the condition, then delegate to true or false branch.""" config = ensure_config(config) callback_manager = get_callback_manager_for_config(config) run_manager = callback_manager.on_chain_start( dumpd(self), input, name=config.get("run_name"), run_id=config.pop("run_id", None), ) final_output: Optional[Output] = None final_output_supported = True try: for idx, branch in enumerate(self.branches): condition, runnable = branch expression_value = condition.invoke( input, config=patch_config( config, callbacks=run_manager.get_child(tag=f"condition:{idx + 1}"), ), ) if expression_value: for chunk in runnable.stream( input, config=patch_config( config, callbacks=run_manager.get_child(tag=f"branch:{idx + 1}"), ), **kwargs, ): yield chunk if final_output_supported: if final_output is None: final_output = chunk else: try: final_output = final_output + chunk # type: ignore except TypeError: final_output = None final_output_supported = False break else: for chunk in self.default.stream( input, config=patch_config( config, callbacks=run_manager.get_child(tag="branch:default"), ), **kwargs, ): yield chunk if final_output_supported: if final_output is None: final_output = chunk else: try: final_output = final_output + chunk # type: ignore except TypeError: final_output = None final_output_supported = False except BaseException as e: run_manager.on_chain_error(e) raise run_manager.on_chain_end(final_output)
[docs] async def astream( self, input: Input, config: Optional[RunnableConfig] = None, **kwargs: Optional[Any], ) -> AsyncIterator[Output]: """First evaluates the condition, then delegate to true or false branch.""" config = ensure_config(config) callback_manager = get_async_callback_manager_for_config(config) run_manager = await callback_manager.on_chain_start( dumpd(self), input, name=config.get("run_name"), run_id=config.pop("run_id", None), ) final_output: Optional[Output] = None final_output_supported = True try: for idx, branch in enumerate(self.branches): condition, runnable = branch expression_value = await condition.ainvoke( input, config=patch_config( config, callbacks=run_manager.get_child(tag=f"condition:{idx + 1}"), ), ) if expression_value: async for chunk in runnable.astream( input, config=patch_config( config, callbacks=run_manager.get_child(tag=f"branch:{idx + 1}"), ), **kwargs, ): yield chunk if final_output_supported: if final_output is None: final_output = chunk else: try: final_output = final_output + chunk # type: ignore except TypeError: final_output = None final_output_supported = False break else: async for chunk in self.default.astream( input, config=patch_config( config, callbacks=run_manager.get_child(tag="branch:default"), ), **kwargs, ): yield chunk if final_output_supported: if final_output is None: final_output = chunk else: try: final_output = final_output + chunk # type: ignore except TypeError: final_output = None final_output_supported = False except BaseException as e: await run_manager.on_chain_error(e) raise await run_manager.on_chain_end(final_output)