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

from app.db.models import Comment

class CommentBase(BaseModel):
    body: str

class CommentCreate(CommentBase):
    post_id: int

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

Here's a breakdown of the file:

2. `CommentBase` is a Pydantic model representing the base fields of a comment (body).
5. `CommentInDBBase` inherits from `CommentBase` and includes additional fields (`id`, `post_id`, `created_at`, and `updated_at`) that are typically stored in the database. The `orm_mode` config is set to `True` to allow reading data from an ORM model.