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
| 38 | |
| 39 | |
| 40 | class RunnableBranch(RunnableSerializable[Input, Output]): |
| 41 | """Runnable that selects which branch to run based on a condition. |
| 42 | |
| 43 | The Runnable is initialized with a list of (condition, Runnable) pairs and |
| 44 | a default branch. |
| 45 | |
| 46 | When operating on an input, the first condition that evaluates to True is |
| 47 | selected, and the corresponding Runnable is run on the input. |
| 48 | |
| 49 | If no condition evaluates to True, the default branch is run on the input. |
| 50 | |
| 51 | Examples: |
| 52 | |
| 53 | .. code-block:: python |
| 54 | |
| 55 | from langchain_core.runnables import RunnableBranch |
| 56 | |
| 57 | branch = RunnableBranch( |
| 58 | (lambda x: isinstance(x, str), lambda x: x.upper()), |
| 59 | (lambda x: isinstance(x, int), lambda x: x + 1), |
| 60 | (lambda x: isinstance(x, float), lambda x: x * 2), |
| 61 | lambda x: "goodbye", |
| 62 | ) |
| 63 | |
| 64 | branch.invoke("hello") # "HELLO" |
| 65 | branch.invoke(None) # "goodbye" |
| 66 | """ |
| 67 | |
| 68 | branches: Sequence[Tuple[Runnable[Input, bool], Runnable[Input, Output]]] |
| 69 | default: Runnable[Input, Output] |
| 70 | |
| 71 | def __init__( |
| 72 | self, |
| 73 | *branches: Union[ |
| 74 | Tuple[ |
| 75 | Union[ |
| 76 | Runnable[Input, bool], |
| 77 | Callable[[Input], bool], |
| 78 | Callable[[Input], Awaitable[bool]], |
| 79 | ], |
| 80 | RunnableLike, |
| 81 | ], |
| 82 | RunnableLike, # To accommodate the default branch |
| 83 | ], |
| 84 | ) -> None: |
| 85 | """A Runnable that runs one of two branches based on a condition.""" |
| 86 | if len(branches) < 2: |
| 87 | raise ValueError("RunnableBranch requires at least two branches") |
| 88 | |
| 89 | default = branches[-1] |
| 90 | |
| 91 | if not isinstance( |
| 92 | default, |
| 93 | (Runnable, Callable, Mapping), # type: ignore[arg-type] |
| 94 | ): |
| 95 | raise TypeError( |
| 96 | "RunnableBranch default must be runnable, callable or mapping." |
| 97 | ) |
no outgoing calls