from typing import (
Any,
Awaitable,
Callable,
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_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]):
"""A 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_)
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"]
@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"),
)
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 Exception 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_callback_manager_for_config(config)
run_manager = callback_manager.on_chain_start(
dumpd(self),
input,
name=config.get("run_name"),
)
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 Exception as e:
run_manager.on_chain_error(e)
raise
run_manager.on_chain_end(dumpd(output))
return output