Here's the `comments.py` file with Pydantic schemas for comments, following the FastAPI project structure with SQLite and SQLAlchemy:


from datetime import datetime
from typing import Optional

from pydantic import BaseModel, Field

class CommentBase(BaseModel):
    content: str = Field(..., min_length=1, max_length=500)

class CommentCreate(CommentBase):
    pass

class CommentUpdate(CommentBase):
    pass

class CommentInDBBase(CommentBase):
    id: int
    post_id: int
    created_at: datetime
    updated_at: Optional[datetime] = None

    class Config:
        orm_mode = True

class Comment(CommentInDBBase):
    pass

class CommentInDB(CommentInDBBase):
    pass

Explanation:

1. We import the necessary modules: `datetime` for working with dates and times, `typing` for type hints, and `pydantic` for defining data models.




5. `CommentInDBBase` inherits from `CommentBase` and adds additional fields for database-related information: `id` (comment ID), `post_id` (ID of the associated post), `created_at` (creation timestamp), and `updated_at` (optional update timestamp). The `Config` class is used to enable the `orm_mode`, which allows Pydantic to work with SQLAlchemy models.