Pydantic Migration Guides
Field(const=True) was removed in Pydantic v2. Use Literal types instead.
Start here
Replace Field(const=True, default=value) with a Literal type annotation. This changes the validation behavior.
Stop before automation when: Choosing the right Literal type for the constant. Fields where the const behavior interacts with validation.
from typing import Literal
from pydantic import BaseModel
class Config(BaseModel):
version: Literal["1.0"] = "1.0"
Repo fit check
Run the matching scanner locally first. Read the free findings and manual alternatives; consider paid cleanup only if supported patterns repeat enough to justify the price.
Example scan summary
supported_findings: 38
manual_review_findings: 6
files_uploaded: 0
confidence: reviewableWhy this page exists
const=True is gone. The replacement depends on how the constant should behave.
Direct answer
Replace Field(const=True, default=value) with a Literal type annotation. This changes the validation behavior.
Example
from pydantic import BaseModel, Field
class Config(BaseModel):
version: str = Field(const=True, default="1.0")
from typing import Literal
from pydantic import BaseModel
class Config(BaseModel):
version: Literal["1.0"] = "1.0"
Decision path
The cleanup pack is strongest when the repo still uses direct pydantic imports and a clean validator/settings/config subset.
Before checkout
Price: $249.99 per team.
Use the exact-problem guides as a triage layer, then decide whether the repo is inside the supported subset.
FAQ
Replace Field(const=True, default=value) with a Literal type annotation. This changes the validation behavior.
Automate only the supported subset: Detection and reporting of Field(const=True) usage. Guidance on the Literal type replacement. Cross-links to other Field parameter changes. Keep these cases in manual review: Choosing the right Literal type for the constant. Fields where the const behavior interacts with validation. Files with other removed Field parameters.
Use Pydantic v1 to v2 Migration Cleanup Pack only when this pattern repeats across enough files that manual cleanup is still costly. Use the free report and upstream guide to evaluate fit. Buy only if repeated supported edits justify the price; no paid assessment is required.
Purchase fit
One matching page is not enough by itself. Run the local scan, then buy only when the same supported pattern appears often enough to matter.
Replace @validator with @field_validator, Move BaseSettings to pydantic-settings, Convert Config to model_config, Replace validate_arguments with validate_call, Replace @root_validator(pre=True) with @model_validator(mode="before"), Why post root validators need manual review, Move pydantic.v1 imports onto pydantic, Why Config.fields is a manual-review case