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NGramOverlapExampleSelector根据ngram重叠得分选择和排序示例，该得分表示示例与输入的相似程度。 ngram重叠得分是一个介于0.0和1.0之间的浮点数。
选择器允许设置阈值得分。 ngram重叠得分小于或等于阈值的示例将被排除。默认情况下，阈值设置为-1.0，因此不会排除任何示例，只会对它们进行重新排序。将阈值设置为0.0将排除具有与输入无ngram重叠的示例。
from langchain.prompts import PromptTemplatefrom langchain.prompts.example_selector.ngram_overlap import NGramOverlapExampleSelectorfrom langchain.prompts import FewShotPromptTemplate, PromptTemplate example_prompt = PromptTemplate( input_variables=["input", "output"], template="Input: {input} Output: {output}",) # These are a lot of examples of a pretend task of creating antonyms.examples = [ {"input": "happy", "output": "sad"}, {"input": "tall", "output": "short"}, {"input": "energetic", "output": "lethargic"}, {"input": "sunny", "output": "gloomy"}, {"input": "windy", "output": "calm"},] # These are examples of a fictional translation task.examples = [ {"input": "See Spot run.", "output": "Ver correr a Spot."}, {"input": "My dog barks.", "output": "Mi perro ladra."}, {"input": "Spot can run.", "output": "Spot puede correr."},] example_prompt = PromptTemplate( input_variables=["input", "output"], template="Input: {input} Output: {output}",)example_selector = NGramOverlapExampleSelector( # These are the examples it has available to choose from. examples=examples, # This is the PromptTemplate being used to format the examples. example_prompt=example_prompt, # This is the threshold, at which selector stops. # It is set to -1.0 by default. threshold=-1.0, # For negative threshold: # Selector sorts examples by ngram overlap score, and excludes none. # For threshold greater than 1.0: # Selector excludes all examples, and returns an empty list. # For threshold equal to 0.0: # Selector sorts examples by ngram overlap score, # and excludes those with no ngram overlap with input.)dynamic_prompt = FewShotPromptTemplate( # We provide an ExampleSelector instead of examples. example_selector=example_selector, example_prompt=example_prompt, prefix="Give the Spanish translation of every input", suffix="Input: {sentence} Output:", input_variables=["sentence"],) # An example input with large ngram overlap with "Spot can run."# and no overlap with "My dog barks."print(dynamic_prompt.format(sentence="Spot can run fast.")) Give the Spanish translation of every input Input: Spot can run.Output: Spot puede correr. Input: See Spot run.Output: Ver correr a Spot. Input: My dog barks.Output: Mi perro ladra. Input: Spot can run fast.Output: # You can add examples to NGramOverlapExampleSelector as well.new_example = {"input": "Spot plays fetch.", "output": "Spot juega a buscar."} example_selector.add_example(new_example)print(dynamic_prompt.format(sentence="Spot can run fast.")) Give the Spanish translation of every input Input: Spot can run.Output: Spot puede correr. Input: See Spot run.Output: Ver correr a Spot. Input: Spot plays fetch.Output: Spot juega a buscar. Input: My dog barks.Output: Mi perro ladra. Input: Spot can run fast.Output: # You can set a threshold at which examples are excluded.# For example, setting threshold equal to 0.0# excludes examples with no ngram overlaps with input.# Since "My dog barks." has no ngram overlaps with "Spot can run fast."# it is excluded.example_selector.threshold=0.0print(dynamic_prompt.format(sentence="Spot can run fast.")) Give the Spanish translation of every input Input: Spot can run.Output: Spot puede correr. Input: See Spot run.Output: Ver correr a Spot. Input: Spot plays fetch.Output: Spot juega a buscar. Input: Spot can run fast.Output: # Setting small nonzero thresholdexample_selector.threshold=0.09print(dynamic_prompt.format(sentence="Spot can play fetch.")) Give the Spanish translation of every input Input: Spot can run.Output: Spot puede correr. Input: Spot plays fetch.Output: Spot juega a buscar. Input: Spot can play fetch.Output: # Setting threshold greater than 1.0example_selector.threshold=1.0+1e-9print(dynamic_prompt.format(sentence="Spot can play fetch.")) Give the Spanish translation of every input Input: Spot can play fetch.Output: 最大边缘相关性（MMR）相似度（Similarity）
