langchain/docs/docs/how_to/example_selectors_ngram.ipynb

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    "# How to select examples by n-gram overlap\n",
    "\n",
    "The `NGramOverlapExampleSelector` selects and orders examples based on which examples are most similar to the input, according to an ngram overlap score. The ngram overlap score is a float between 0.0 and 1.0, inclusive. \n",
    "\n",
    "The selector allows for a threshold score to be set. Examples with an ngram overlap score less than or equal to the threshold are excluded. The threshold is set to -1.0, by default, so will not exclude any examples, only reorder them. Setting the threshold to 0.0 will exclude examples that have no ngram overlaps with the input.\n"
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    "from langchain_community.example_selectors import NGramOverlapExampleSelector\n",
    "from langchain_core.prompts import FewShotPromptTemplate, PromptTemplate\n",
    "\n",
    "example_prompt = PromptTemplate(\n",
    "    input_variables=[\"input\", \"output\"],\n",
    "    template=\"Input: {input}\\nOutput: {output}\",\n",
    ")\n",
    "\n",
    "# Examples of a fictional translation task.\n",
    "examples = [\n",
    "    {\"input\": \"See Spot run.\", \"output\": \"Ver correr a Spot.\"},\n",
    "    {\"input\": \"My dog barks.\", \"output\": \"Mi perro ladra.\"},\n",
    "    {\"input\": \"Spot can run.\", \"output\": \"Spot puede correr.\"},\n",
    "]"
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    "example_selector = NGramOverlapExampleSelector(\n",
    "    # The examples it has available to choose from.\n",
    "    examples=examples,\n",
    "    # The PromptTemplate being used to format the examples.\n",
    "    example_prompt=example_prompt,\n",
    "    # The threshold, at which selector stops.\n",
    "    # It is set to -1.0 by default.\n",
    "    threshold=-1.0,\n",
    "    # For negative threshold:\n",
    "    # Selector sorts examples by ngram overlap score, and excludes none.\n",
    "    # For threshold greater than 1.0:\n",
    "    # Selector excludes all examples, and returns an empty list.\n",
    "    # For threshold equal to 0.0:\n",
    "    # Selector sorts examples by ngram overlap score,\n",
    "    # and excludes those with no ngram overlap with input.\n",
    ")\n",
    "dynamic_prompt = FewShotPromptTemplate(\n",
    "    # We provide an ExampleSelector instead of examples.\n",
    "    example_selector=example_selector,\n",
    "    example_prompt=example_prompt,\n",
    "    prefix=\"Give the Spanish translation of every input\",\n",
    "    suffix=\"Input: {sentence}\\nOutput:\",\n",
    "    input_variables=[\"sentence\"],\n",
    ")"
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     "text": [
      "Give the Spanish translation of every input\n",
      "\n",
      "Input: Spot can run.\n",
      "Output: Spot puede correr.\n",
      "\n",
      "Input: See Spot run.\n",
      "Output: Ver correr a Spot.\n",
      "\n",
      "Input: My dog barks.\n",
      "Output: Mi perro ladra.\n",
      "\n",
      "Input: Spot can run fast.\n",
      "Output:\n"
     ]
    }
   ],
   "source": [
    "# An example input with large ngram overlap with \"Spot can run.\"\n",
    "# and no overlap with \"My dog barks.\"\n",
    "print(dynamic_prompt.format(sentence=\"Spot can run fast.\"))"
   ]
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      "Give the Spanish translation of every input\n",
      "\n",
      "Input: Spot can run.\n",
      "Output: Spot puede correr.\n",
      "\n",
      "Input: See Spot run.\n",
      "Output: Ver correr a Spot.\n",
      "\n",
      "Input: Spot plays fetch.\n",
      "Output: Spot juega a buscar.\n",
      "\n",
      "Input: My dog barks.\n",
      "Output: Mi perro ladra.\n",
      "\n",
      "Input: Spot can run fast.\n",
      "Output:\n"
     ]
    }
   ],
   "source": [
    "# You can add examples to NGramOverlapExampleSelector as well.\n",
    "new_example = {\"input\": \"Spot plays fetch.\", \"output\": \"Spot juega a buscar.\"}\n",
    "\n",
    "example_selector.add_example(new_example)\n",
    "print(dynamic_prompt.format(sentence=\"Spot can run fast.\"))"
   ]
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      "Give the Spanish translation of every input\n",
      "\n",
      "Input: Spot can run.\n",
      "Output: Spot puede correr.\n",
      "\n",
      "Input: See Spot run.\n",
      "Output: Ver correr a Spot.\n",
      "\n",
      "Input: Spot plays fetch.\n",
      "Output: Spot juega a buscar.\n",
      "\n",
      "Input: Spot can run fast.\n",
      "Output:\n"
     ]
    }
   ],
   "source": [
    "# You can set a threshold at which examples are excluded.\n",
    "# For example, setting threshold equal to 0.0\n",
    "# excludes examples with no ngram overlaps with input.\n",
    "# Since \"My dog barks.\" has no ngram overlaps with \"Spot can run fast.\"\n",
    "# it is excluded.\n",
    "example_selector.threshold = 0.0\n",
    "print(dynamic_prompt.format(sentence=\"Spot can run fast.\"))"
   ]
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   "cell_type": "code",
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     "text": [
      "Give the Spanish translation of every input\n",
      "\n",
      "Input: Spot can run.\n",
      "Output: Spot puede correr.\n",
      "\n",
      "Input: Spot plays fetch.\n",
      "Output: Spot juega a buscar.\n",
      "\n",
      "Input: Spot can play fetch.\n",
      "Output:\n"
     ]
    }
   ],
   "source": [
    "# Setting small nonzero threshold\n",
    "example_selector.threshold = 0.09\n",
    "print(dynamic_prompt.format(sentence=\"Spot can play fetch.\"))"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 8,
   "id": "09633aa8",
   "metadata": {},
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     "name": "stdout",
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     "text": [
      "Give the Spanish translation of every input\n",
      "\n",
      "Input: Spot can play fetch.\n",
      "Output:\n"
     ]
    }
   ],
   "source": [
    "# Setting threshold greater than 1.0\n",
    "example_selector.threshold = 1.0 + 1e-9\n",
    "print(dynamic_prompt.format(sentence=\"Spot can play fetch.\"))"
   ]
  },
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