Pydantic models in Python

A model validates and coerces on construction, from a class of annotations.

from pydantic import BaseModel, ValidationError


class Run(BaseModel):
    lang: str
    tpm: float
    stars: int = 1


run = Run(lang="python", tpm="104.5", stars=3)
print(run.tpm, type(run.tpm).__name__)
print(run.model_dump())
print(run.model_dump_json())

try:
    Run(lang="rust", tpm="fast")
except ValidationError as exc:
    print(exc.error_count(), exc.errors()[0]["loc"], exc.errors()[0]["type"])

How it works

1. Types are enforced: a numeric string becomes an int.
2. model_dump and model_dump_json serialize it back.
3. A bad value raises ValidationError with the field named.

Keywords and builtins used here

• Run
• as
• class
• except
• float
• int
• print
• str
• try
• type

The run, in numbers

Lines

18

Characters to type

388

Tokens

131

Three-star pace

105 tpm

At the three-star pace of 105 tokens a minute, this run takes about 75 seconds.

Type this snippet

Step 1 of 5 in Pydantic models, step 1 of 19 in Web services & data access.

Next →