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CoreyMSchafer/main.py

Created October 27, 2025 14:08
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Pydantic Tutorial Code
Raw
main.py
import json
from datetime import UTC, datetime
from functools import partial
from typing import Annotated, Literal
from uuid import UUID, uuid4
from pydantic import (
BaseModel,
ConfigDict,
EmailStr,
Field,
HttpUrl,
SecretStr,
ValidationError,
ValidationInfo,
computed_field,
field_validator,
model_validator,
)
class User(BaseModel):
model_config = ConfigDict(
populate_by_name=True,
strict=True,
extra="allow",
frozen=True,
)
uid: UUID = Field(alias="id", default_factory=uuid4)
username: Annotated[str, Field(min_length=3, max_length=20)]
email: EmailStr
password: SecretStr
website: HttpUrl | None = None
age: Annotated[int, Field(ge=13, le=130)]
verified_at: datetime | None = None
bio: str = ""
is_active: bool = True
first_name: str = ""
last_name: str = ""
follower_count: int = 0
@field_validator("username")
@classmethod
def validate_username(cls, v: str) -> str:
if not v.replace("_", "").isalnum():
raise ValueError("Username must be alphanumeric (underscores allowed)")
return v.lower()
@field_validator("website", mode="before")
@classmethod
def add_https(cls, v: str | None) -> str | None:
if v and not v.startswith(("http://", "https://")):
return f"https://{v}"
return v
@computed_field
@property
def display_name(self) -> str:
if self.first_name and self.last_name:
return f"{self.first_name} {self.last_name}"
return self.username
@computed_field
@property
def is_influencer(self) -> bool:
return self.follower_count >= 10000
class Comment(BaseModel):
content: str
author_email: EmailStr
likes: int = 0
class BlogPost(BaseModel):
title: Annotated[str, Field(min_length=1, max_length=200)]
content: Annotated[str, Field(min_length=10)]
author: User
view_count: int = 0
is_published: bool = False
tags: list[str] = Field(default_factory=list)
create_at: datetime = Field(default_factory=partial(datetime.now, tz=UTC))
status: Literal["draft", "published", "archived"] = "draft"
slug: Annotated[str, Field(pattern=r"^[a-z0-9-]+$")]
comments: list[Comment] = Field(default_factory=list)
class UserRegistration(BaseModel):
email: EmailStr
password: str
confirm_password: str
@model_validator(mode="after")
def passwords_match(self) -> "UserRegistration":
if self.password != self.confirm_password:
raise ValueError("Passwords do not match")
return self
user_data = {
"id": "3bc4bf25-1b73-44da-9078-f2bb310c7374",
"username": "Corey_Schafer",
"email": "[email protected]",
"age": 39,
"password": "secret123",
"notes": "Kind've a Karen...",
}
user = User.model_validate_json(json.dumps(user_data))
user.email = "[email protected]"
print(user.model_dump_json(indent=2))
Raw
snippets.txt
### New BlogPost
post = BlogPost(
title="Getting Started with Python",
content="Here's how to begin...",
author_id="12345",
)
### Invalid User
try:
user = User(
uid=0,
username="cs",
email="[email protected]",
age=12,
)
except ValidationError as e:
print(e)
### Valid User
user = User(
username="coreyms",
email="[email protected]",
age=39,
password="secret123",
)
print(user)
### Username Validation
@field_validator('username')
@classmethod
def validate_username(cls, v: str) -> str:
if not v.replace('_', '').isalnum():
raise ValueError('Username must be alphanumeric (underscores allowed)')
return v.lower()
### URL Validation (no mode)
@field_validator('website')
@classmethod
def add_https(cls, v: str | None) -> str | None:
if v and not v.startswith(('http://', 'https://')):
return f'https://{v}'
return v
### Model Validator
class UserRegistration(BaseModel):
email: EmailStr
password: str
confirm_password: str
@model_validator(mode='after')
def passwords_match(self) -> 'UserRegistration':
if self.password != self.confirm_password:
raise ValueError('Passwords do not match')
return self
try:
registration = UserRegistration(
email="[email protected]",
password="secret123",
confirm_password="secret456"
)
except ValidationError as e:
print(e)
### Computed Fields
first_name: str = ""
last_name: str = ""
follower_count: int = 0
@computed_field
@property
def display_name(self) -> str:
if self.first_name and self.last_name:
return f"{self.first_name} {self.last_name}"
return self.username
@computed_field
@property
def is_influencer(self) -> bool:
return self.follower_count >= 10000
### Comment Model
class Comment(BaseModel):
content: str
author_email: EmailStr
likes: int = 0
### BlogPost Dictionary
post_data = {
"title": "Understanding Pydantic Models",
"content": "Pydantic makes data validation easy and intuitive...",
"slug": "understanding-pydantic",
"author": {
"username": "coreyms",
"email": "[email protected]",
"age": 39,
"password": "secret123",
},
"comments": [
{
"content": "I think I understand nested models now!",
"author_email": "[email protected]",
"likes": 25,
},
{
"content": "Can you cover FastAPI next?",
"author_email": "[email protected]",
"likes": 15,
},
],
}
post = BlogPost(**post_data)
print(post.model_dump_json(indent=2))
### User Dictionary
user_data = {
"id": "3bc4bf25-1b73-44da-9078-f2bb310c7374",
"username": "Corey_Schafer",
"email": "[email protected]",
"age": "39",
"password": "secret123",
}
user = User.model_validate(user_data)
print(user.model_dump_json(indent=2))
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