Pydantic: constr: Constrain string values

‘constr’ type method is used to constraining str values. Below table summarizes the arguments of ‘constr’ method.

 

Argument	Data type	Description
strip_whitespace	bool = False	removes leading and trailing whitespace
to_lower	bool = False	turns all characters to lowercase
strict	bool = False	controls type coercion
min_length	int = None	minimum length of the string
max_length	int = None	maximum length of the string
curtail_length	int = None	shrinks the string length to the set value when it is longer than the set value
regex	str = None	regex to validate the string against

 

Example

class Box(BaseModel):
    id: int
    address: constr(to_lower=True)

 

Find the below working application.

 

constr_demo_1.py

 

from pydantic import (
    BaseModel,
    constr,
    ValidationError
)

class Box(BaseModel):
    id: int
    address: constr(to_lower=True)

try:
    box1 = Box(id = 1, address='BANAGALORE, Chodeswari street')
    print(box1.json())
except ValidationError as e:
    print(e.json())

 

Output

{"id": 1, "address": "banagalore, chodeswari street"}

  

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