python data_error ai_generated true

pydantic_core._pydantic_core.ValidationError: 1 validation error for Price value Decimal input should have no more than 2 decimal places [type=decimal_max_places, input_value='1.2345', input_type=str]

ID: python/pydantic-decimal-max-digits

Also available as: JSON · Markdown · 中文
80%Fix Rate
87%Confidence
0Evidence
2024-09-05First Seen

Version Compatibility

VersionStatusIntroducedDeprecatedNotes
2.x active — — —

Root Cause

A Decimal field declared with max_digits/decimal_places received a value with more fractional digits than allowed.

generic

中文

声明了 max_digits/decimal_places 的 Decimal 字段接收到了小数位数超过限制的值。

Workarounds

  1. 92% success 
    from decimal import Decimal, ROUND_HALF_UP
v = Decimal('1.2345').quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)
Price(value=v)
  2. 90% success 
    from pydantic import BaseModel, field_validator, Field
from decimal import Decimal, ROUND_HALF_UP
class Price(BaseModel):
    value: Decimal = Field(max_digits=10, decimal_places=2)
    @field_validator('value', mode='before')
    @classmethod
    def quantize(cls, v):
        return Decimal(str(v)).quantize(Decimal('0.01'), rounding=ROUND_HALF_UP)

Dead Ends

Common approaches that don't work:

  1. 60% fail

    Introduces binary floating-point rounding; 1.2345 becomes 1.2344999...

  2. 50% fail

    Defeats the purpose and allows inconsistent money precision downstream.

  3. 70% fail

    Silently zeroes real prices, causing financial data corruption.