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68 lines
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68 lines
2.0 KiB
Markdown
# Create a custom example selector
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In this tutorial, we'll create a custom example selector that selects examples every alternate example given a list of examples.
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An `ExampleSelector` must implement two methods:
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1. An `add_example` method which takes in an example and adds it into the ExampleSelector
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2. A `select_examples` method which takes in input variables (which are meant to be user input) and returns a list of examples to use in the few shot prompt.
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Let's implement a custom `ExampleSelector` that just selects two examples at random.
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:::{note}
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Take a look at the current set of example selector implementations supported in LangChain [here](../getting_started.md).
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:::
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<!-- TODO(shreya): Add the correct link. -->
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## Implement custom example selector
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```python
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from langchain.prompts.example_selector.base import BaseExampleSelector
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from typing import Dict, List
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import numpy as np
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class CustomExampleSelector(BaseExampleSelector):
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def __init__(self, examples: List[Dict[str, str]]):
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self.examples = examples
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def add_example(self, example: Dict[str, str]) -> None:
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"""Add new example to store for a key."""
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self.examples.append(example)
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def select_examples(self, input_variables: Dict[str, str]) -> List[dict]:
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"""Select which examples to use based on the inputs."""
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return np.random.choice(self.examples, size=2, replace=False)
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```
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## Use custom example selector
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```python
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examples = [
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{"foo": "1"},
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{"foo": "2"},
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{"foo": "3"}
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]
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# Initialize example selector.
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example_selector = CustomExampleSelector(examples)
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# Select examples
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example_selector.select_examples({"foo": "foo"})
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# -> array([{'foo': '2'}, {'foo': '3'}], dtype=object)
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# Add new example to the set of examples
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example_selector.add_example({"foo": "4"})
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example_selector.examples
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# -> [{'foo': '1'}, {'foo': '2'}, {'foo': '3'}, {'foo': '4'}]
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# Select examples
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example_selector.select_examples({"foo": "foo"})
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# -> array([{'foo': '1'}, {'foo': '4'}], dtype=object)
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``` |