Pydantic

Pydantic is a Python library focused on data parsing and validation, leveraging Python’s type hints. I feel it is to python what typescript is to javascript but there is some differences

Examples from their page


from datetime import datetime

from pydantic import BaseModel, PositiveInt


class User(BaseModel):
    id: int  
    name: str = 'John Doe'  
    signup_ts: datetime | None  
    tastes: dict[str, PositiveInt]  


external_data = {
    'id': 123,
    'signup_ts': '2019-06-01 12:22',  
    'tastes': {
        'wine': 9,
        b'cheese': 7,  
        'cabbage': '1',  
    },
}

user = User(**external_data)  

print(user.id)  
#> 123
print(user.model_dump())  
"""
{
    'id': 123,
    'name': 'John Doe',
    'signup_ts': datetime.datetime(2019, 6, 1, 12, 22),
    'tastes': {'wine': 9, 'cheese': 7, 'cabbage': 1},
}
"""

Error


# continuing the above example...

from datetime import datetime
from pydantic import BaseModel, PositiveInt, ValidationError


class User(BaseModel):
    id: int
    name: str = 'John Doe'
    signup_ts: datetime | None
    tastes: dict[str, PositiveInt]


external_data = {'id': 'not an int', 'tastes': {}}  

try:
    User(**external_data)  
except ValidationError as e:
    print(e.errors())
    """
    [
        {
            'type': 'int_parsing',
            'loc': ('id',),
            'msg': 'Input should be a valid integer, unable to parse string as an integer',
            'input': 'not an int',
            'url': 'https://errors.pydantic.dev/2/v/int_parsing',
        },
        {
            'type': 'missing',
            'loc': ('signup_ts',),
            'msg': 'Field required',
            'input': {'id': 'not an int', 'tastes': {}},
            'url': 'https://errors.pydantic.dev/2/v/missing',
        },
    ]
    """