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explore / Backend & APIs / mozg / Pydantic

Pydantic · Concepts

Answer questions about the Pydantic concepts: models and their config, fields and aliases, validators and serializers, dataclasses, JSON Schema, strict mode, type adapters, and how each standard and custom type is coerced.

422 notes · updated 2026-08-10 · trained 82%

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https://mozg.sh/mcp --header "Authorization: Bearer …"
> use mozg/pydantic-concepts — …
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Ask it things like

answers 25/30 on its latest exam
What does model_construct() do, and how does it handle extra data?Models✓
What is the purpose of TypeAdapter?Type Adapters✓
What are the four types of field validators in Pydantic?Validators✓
What does arbitrary_types_allowed do when set to True?Configuration✓
What is the difference between extra='forbid' and extra='ignore'?Configuration✓
What is the difference between Pydantic dataclasses and Python stdlib dataclasses?Configuration✓
What happens when you call model_dump(by_alias=True)?Fields & Aliases✓
What is the difference between exclude_defaults and exclude_none in model_dump()?Fields & Aliases✓

What it can answer

30 coverage checks
82%
Answers 25 of the exam's 30 questionsIt answers 25 questions, the same as last time.
▲Fields & Aliases4 / 5
✓Type Coercion4 / 4
✓Validators4 / 4
▲Configuration3 / 4
✓Serializers3 / 3
✓Strict Mode3 / 3
✓JSON Schema2 / 2
▲Models1 / 4
✓Type Adapters1 / 1
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Attacks survived

re-run weekly · 2026-08-10
✓gate-battery12/12 known hostile payloads caught by the ingest gate
✓injection-corpusevery active note scanned — no steering language
✓secret-corpusevery active note scanned — no keys or credentials

heuristic scans against known attack classes — measured and dated, not a promise of unpoisonability

Inside

  • Prefer after validators over before validators · validators
  • Recursive type aliases with TypeAliasType · models
  • Assignment form vs Annotated pattern for Field · fields & aliases
  • StringConstraints for string-specific constraints · type coercion
  • Avoid unions for type coercion · type coercion
  • Avoid from __future__ import annotations in Pydantic modules · models
  • Pydantic purpose and use cases · models
  • Field metadata types: field-specific vs type-specific · fields & aliases
  • Field-specific metadata must apply to whole union type · fields & aliases
  • Use built-in validation constraints instead of custom validators · validators
  • Annotated pattern for validators over decorator pattern · validators
  • Type coercion in non-strict mode · strict mode
  • Avoid abstract collections types · type coercion
  • Subclass serialization uses defined type not runtime value · models

Licence

CC BY-NC-SA 4.0

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