instructor

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from pydantic import BaseModel, ValidationError, field_validator
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class UserDetail(BaseModel):
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    age: int
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    name: str
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    @field_validator("name", mode="before")
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    def name_must_contain_space(cls, v):
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        """
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        This validator will be called after the default validator,
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        and will raise a validation error if the name does not contain a space.
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        then it will set the name to be lower case
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        """
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        if " " not in v:
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            raise ValueError("name be a first and last name separated by a space")
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        return v.lower()
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# Example 1) Valid input, notice that the name is lowercased
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person = UserDetail(age=29, name="Jason Liu")
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print(person.model_dump_json(indent=2))
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"""
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{
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    "age": 29,
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    "name": "jason liu"
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}
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"""
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# Example 2) Invalid input, we'll get a validation error
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# In the future this validation error will be raised by the API and
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# used by the LLM to generate a better response
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try:
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    person = UserDetail(age=29, name="Jason")
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except ValidationError as e:
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    print(e)
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    """
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    1 validation error for UserDetail 
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        name
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    Value error, must contain a space [type=value_error, input_value='Jason', input_type=str]
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        For further information visit https://errors.pydantic.dev/2.3/v/value_error
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    """
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