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Pydantic & Validation interview questions

24 real Pydantic & Validation questions from the FastAPI bank, as asked in Indian campus drives and tech interviews. Every question has a verified answer and an AI-tutor explanation on placd — free to start.

1. What is BaseModel?

Junior
  1. A.the mechanism where Python annotations are enforced at runtime, rejecting requests whose data cannot be coerced to the declared types
  2. B.the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
  3. C.the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
  4. D.the Pydantic class subclassed to declare a data schema, giving automatic parsing, validation, and serialization from type hints
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2. Which term means: "the Pydantic class subclassed to declare a data schema, giving automatic parsing, validation, and serialization from type hints"?

Junior
  1. A.Type-hint validation
  2. B.BaseModel
  3. C.model_config
  4. D.Pydantic v2 rewrite
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3. Which statement is correct?

Junior
  1. A.BaseModel — the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
  2. B.BaseModel — the class attribute, typically a ConfigDict, that sets schema behavior such as forbidding extra keys or enabling attribute reading
  3. C.BaseModel — the Pydantic class subclassed to declare a data schema, giving automatic parsing, validation, and serialization from type hints
  4. D.BaseModel — the Pydantic v2 decorator for a method that checks or transforms one named attribute after its type is parsed
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4. What is Type-hint validation?

Junior
  1. A.the Pydantic class subclassed to declare a data schema, giving automatic parsing, validation, and serialization from type hints
  2. B.the Pydantic v2 decorator for a method that validates the whole object, allowing checks that span multiple attributes
  3. C.the Pydantic v2 decorator for a method that checks or transforms one named attribute after its type is parsed
  4. D.the mechanism where Python annotations are enforced at runtime, rejecting requests whose data cannot be coerced to the declared types
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5. Which term means: "the mechanism where Python annotations are enforced at runtime, rejecting requests whose data cannot be coerced to the declared types"?

Junior
  1. A.BaseModel
  2. B.Pydantic v2 rewrite
  3. C.Type-hint validation
  4. D.model_validator
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6. Which statement is correct?

Junior
  1. A.Type-hint validation — the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute
  2. B.Type-hint validation — the Pydantic v2 decorator for a method that checks or transforms one named attribute after its type is parsed
  3. C.Type-hint validation — the mechanism where Python annotations are enforced at runtime, rejecting requests whose data cannot be coerced to the declared types
  4. D.Type-hint validation — the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
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7. What is Field?

Mid
  1. A.the Pydantic class subclassed to declare a data schema, giving automatic parsing, validation, and serialization from type hints
  2. B.the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
  3. C.the Pydantic v2 decorator for a method that checks or transforms one named attribute after its type is parsed
  4. D.the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute
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8. Which term means: "the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute"?

Mid
  1. A.Field
  2. B.Pydantic v2 rewrite
  3. C.Type-hint validation
  4. D.field_validator
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9. Which statement is correct?

Mid
  1. A.Field — the Pydantic class subclassed to declare a data schema, giving automatic parsing, validation, and serialization from type hints
  2. B.Field — the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute
  3. C.Field — the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
  4. D.Field — the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
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10. What is field_validator?

Mid
  1. A.the Pydantic v2 decorator for a method that checks or transforms one named attribute after its type is parsed
  2. B.the class attribute, typically a ConfigDict, that sets schema behavior such as forbidding extra keys or enabling attribute reading
  3. C.the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
  4. D.the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute
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12. Which statement is correct?

Mid
  1. A.field_validator — the mechanism where Python annotations are enforced at runtime, rejecting requests whose data cannot be coerced to the declared types
  2. B.field_validator — the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
  3. C.field_validator — the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
  4. D.field_validator — the Pydantic v2 decorator for a method that checks or transforms one named attribute after its type is parsed
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13. What is model_validator?

Senior
  1. A.the Pydantic class subclassed to declare a data schema, giving automatic parsing, validation, and serialization from type hints
  2. B.the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute
  3. C.the Pydantic v2 decorator for a method that validates the whole object, allowing checks that span multiple attributes
  4. D.the class attribute, typically a ConfigDict, that sets schema behavior such as forbidding extra keys or enabling attribute reading
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14. Which term means: "the Pydantic v2 decorator for a method that validates the whole object, allowing checks that span multiple attributes"?

Senior
  1. A.Type-hint validation
  2. B.model_validator
  3. C.BaseModel
  4. D.model_dump
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15. Which statement is correct?

Senior
  1. A.model_validator — the Pydantic v2 decorator for a method that checks or transforms one named attribute after its type is parsed
  2. B.model_validator — the Pydantic v2 decorator for a method that validates the whole object, allowing checks that span multiple attributes
  3. C.model_validator — the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute
  4. D.model_validator — the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
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16. What is model_config?

Senior
  1. A.the class attribute, typically a ConfigDict, that sets schema behavior such as forbidding extra keys or enabling attribute reading
  2. B.the mechanism where Python annotations are enforced at runtime, rejecting requests whose data cannot be coerced to the declared types
  3. C.the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute
  4. D.the Pydantic v2 decorator for a method that validates the whole object, allowing checks that span multiple attributes
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17. Which term means: "the class attribute, typically a ConfigDict, that sets schema behavior such as forbidding extra keys or enabling attribute reading"?

Senior
  1. A.field_validator
  2. B.model_dump
  3. C.Type-hint validation
  4. D.model_config
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18. Which statement is correct?

Senior
  1. A.model_config — the class attribute, typically a ConfigDict, that sets schema behavior such as forbidding extra keys or enabling attribute reading
  2. B.model_config — the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
  3. C.model_config — the Pydantic v2 decorator for a method that checks or transforms one named attribute after its type is parsed
  4. D.model_config — the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
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19. What is model_dump?

Mid
  1. A.the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute
  2. B.the class attribute, typically a ConfigDict, that sets schema behavior such as forbidding extra keys or enabling attribute reading
  3. C.the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
  4. D.the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
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21. Which statement is correct?

Mid
  1. A.model_dump — the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
  2. B.model_dump — the Pydantic v2 decorator for a method that validates the whole object, allowing checks that span multiple attributes
  3. C.model_dump — the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
  4. D.model_dump — the Pydantic class subclassed to declare a data schema, giving automatic parsing, validation, and serialization from type hints
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22. What is Pydantic v2 rewrite?

Senior
  1. A.the Pydantic class subclassed to declare a data schema, giving automatic parsing, validation, and serialization from type hints
  2. B.the Pydantic v2 decorator for a method that checks or transforms one named attribute after its type is parsed
  3. C.the helper that attaches metadata and constraints like gt, max_length, default, and description to a single model attribute
  4. D.the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
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23. Which term means: "the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys"?

Senior
  1. A.field_validator
  2. B.model_dump
  3. C.Pydantic v2 rewrite
  4. D.model_validator
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24. Which statement is correct?

Senior
  1. A.Pydantic v2 rewrite — the mechanism where Python annotations are enforced at runtime, rejecting requests whose data cannot be coerced to the declared types
  2. B.Pydantic v2 rewrite — the Pydantic v2 decorator for a method that validates the whole object, allowing checks that span multiple attributes
  3. C.Pydantic v2 rewrite — the version whose core was reimplemented in Rust for major speed gains, renaming many v1 methods and config keys
  4. D.Pydantic v2 rewrite — the Pydantic v2 method that serializes an instance to a plain dictionary, replacing the v1 dict method
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