pip install pydantic

import pydantic
print('compiled:', pydantic.compiled)

pip install pydantic[dotenv]

from pydantic import BaseModel
class User(BaseModel):
? ? id: int
? ? name = 'Jane Doe

user = User(id='123')

from typing import List
from pydantic import BaseModel
class Foo(BaseModel):
? ? count: int
? ? size: float = None
class Bar(BaseModel):
? ? apple = 'x'
? ? banana = 'y'
class Spam(BaseModel):
? ? foo: Foo
? ? bars: List[Bar]

from typing import Generic, TypeVar, Optional, List
from pydantic import BaseModel, validator, ValidationError
from pydantic.generics import GenericModel
DataT = TypeVar('DataT')
class Error(BaseModel):
? ? code: int
? ? message: str
class DataModel(BaseModel):
? ? numbers: List[int]
? ? people: List[str]
class Response(GenericModel, Generic[DataT]):
? ? data: Optional[DataT]
? ? error: Optional[Error]
? ? @validator('error', always=True)
? ? def check_consistency(cls, v, values):
? ? ? ? if v is not None and values['data'] is not None:
? ? ? ? ? ? raise ValueError('must not provide both data and error')
? ? ? ? if v is None and values.get('data') is None:
? ? ? ? ? ? raise ValueError('must provide data or error')
? ? ? ? return v
data = DataModel(numbers=[1, 2, 3], people=[])
error = Error(code=404, message='Not found')
print(Response[int](data=1))
#> data=1 error=None
print(Response[str](data='value'))
#> data='value' error=None
print(Response[str](data='value').dict())
#> {'data': 'value', 'error': None}
print(Response[DataModel](data=data).dict())
"""
{
? ? 'data': {'numbers': [1, 2, 3], 'people': []},
? ? 'error': None,
}
"""
print(Response[DataModel](error=error).dict())
"""
{
? ? 'data': None,
? ? 'error': {'code': 404, 'message': 'Not found'},
}
"""
try:
? ? Response[int](data='value')
except ValidationError as e:
? ? print(e)
? ? """
? ? 2 validation errors for Response[int]
? ? data
? ? ? value is not a valid integer (type=type_error.integer)
? ? error
? ? ? must provide data or error (type=value_error)
? ? """

from pydantic import BaseModel, create_model
DynamicFoobarModel = create_model('DynamicFoobarModel', foo=(str, ...), bar=123)

from pydantic import BaseModel, ValidationError, validator
class UserModel(BaseModel):
? ? name: str
? ? username: str
? ? password1: str
? ? password2: str
? ? @validator('name')
? ? def name_must_contain_space(cls, v):
? ? ? ? if ' ' not in v:
? ? ? ? ? ? raise ValueError('must contain a space')
? ? ? ? return v.title()
? ? @validator('password2')
? ? def passwords_match(cls, v, values, **kwargs):
? ? ? ? if 'password1' in values and v != values['password1']:
? ? ? ? ? ? raise ValueError('passwords do not match')
? ? ? ? return v
? ? @validator('username')
? ? def username_alphanumeric(cls, v):
? ? ? ? assert v.isalnum(), 'must be alphanumeric'
? ? ? ? return v
user = UserModel(
? ? name='samuel colvin',
? ? username='scolvin',
? ? password1='zxcvbn',
? ? password2='zxcvbn',
)
print(user)
#> name='Samuel Colvin' username='scolvin' password1='zxcvbn' password2='zxcvbn'
try:
? ? UserModel(
? ? ? ? name='samuel',
? ? ? ? username='scolvin',
? ? ? ? password1='zxcvbn',
? ? ? ? password2='zxcvbn2',
? ? )
except ValidationError as e:
? ? print(e)
? ? """
? ? 2 validation errors for UserModel
? ? name
? ? ? must contain a space (type=value_error)
? ? password2
? ? ? passwords do not match (type=value_error)
? ? """

from typing import List
from pydantic import BaseModel, ValidationError, validator
class ParentModel(BaseModel):
? ? names: List[str]
class ChildModel(ParentModel):
? ? @validator('names', each_item=True)
? ? def check_names_not_empty(cls, v):
? ? ? ? assert v != '', 'Empty strings are not allowed.'
? ? ? ? return v
# This will NOT raise a ValidationError because the validator was not called
try:
? ? child = ChildModel(names=['Alice', 'Bob', 'Eve', ''])
except ValidationError as e:
? ? print(e)
else:
? ? print('No ValidationError caught.')
? ? #> No ValidationError caught.
class ChildModel2(ParentModel):
? ? @validator('names')
? ? def check_names_not_empty(cls, v):
? ? ? ? for name in v:
? ? ? ? ? ? assert name != '', 'Empty strings are not allowed.'
? ? ? ? return v
try:
? ? child = ChildModel2(names=['Alice', 'Bob', 'Eve', ''])
except ValidationError as e:
? ? print(e)
? ? """
? ? 1 validation error for ChildModel2
? ? names
? ? ? Empty strings are not allowed. (type=assertion_error)
? ? """

from pydantic import BaseModel, validator
def normalize(name: str) -> str:
? ? return ' '.join((word.capitalize()) for word in name.split(' '))
class Producer(BaseModel):
? ? name: str
? ? # validators
? ? _normalize_name = validator('name', allow_reuse=True)(normalize)
class Consumer(BaseModel):
? ? name: str
? ? # validators
? ? _normalize_name = validator('name', allow_reuse=True)(normalize)

from typing import Set
from pydantic import (
? ? BaseModel,
? ? BaseSettings,
? ? PyObject,
? ? RedisDsn,
? ? PostgresDsn,
? ? Field,
)
class SubModel(BaseModel):
? ? foo = 'bar'
? ? apple = 1
class Settings(BaseSettings):
? ? auth_key: str
? ? api_key: str = Field(..., env='my_api_key')
? ? redis_dsn: RedisDsn = 'redis://user:pass@localhost:6379/1'
? ? pg_dsn: PostgresDsn = 'postgres://user:pass@localhost:5432/foobar'
? ? special_function: PyObject = 'math.cos'
? ? # to override domains:
? ? # export my_prefix_domains='["foo.com", "bar.com"]'
? ? domains: Set[str] = set()
? ? # to override more_settings:
? ? # export my_prefix_more_settings='{"foo": "x", "apple": 1}'
? ? more_settings: SubModel = SubModel()
? ? class Config:
? ? ? ? env_prefix = 'my_prefix_' ?# defaults to no prefix, i.e. ""
? ? ? ? fields = {
? ? ? ? ? ? 'auth_key': {
? ? ? ? ? ? ? ? 'env': 'my_auth_key',
? ? ? ? ? ? },
? ? ? ? ? ? 'redis_dsn': {
? ? ? ? ? ? ? ? 'env': ['service_redis_dsn', 'redis_url']
? ? ? ? ? ? }
? ? ? ? }
print(Settings().dict())
"""
{
? ? 'auth_key': 'xxx',
? ? 'api_key': 'xxx',
? ? 'redis_dsn': RedisDsn('redis://user:pass@localhost:6379/1',
scheme='redis', user='user', password='pass', host='localhost',
host_type='int_domain', port='6379', path='/1'),
? ? 'pg_dsn': PostgresDsn('postgres://user:pass@localhost:5432/foobar',
scheme='postgres', user='user', password='pass', host='localhost',
host_type='int_domain', port='5432', path='/foobar'),
? ? 'special_function': <built-in function cos>,
? ? 'domains': set(),
? ? 'more_settings': {'foo': 'bar', 'apple': 1},
}
"""

class Settings(BaseSettings):
? ? ...
? ? class Config:
? ? ? ? env_file = '.env'
? ? ? ? env_file_encoding = 'utf-8'

settings=Settings(_env_file='prod.env',_env_file_encoding='utf-8')

class Settings(BaseSettings):
? ? ...
? ? database_password: str
? ? class Config:
? ? ? ? secrets_dir = '/var/run'

settings = Settings(_secrets_dir='/var/run')

from datetime import datetime
from typing import List, Optional
from pydantic import BaseModel, NoneStr
class Model(BaseModel):
? ? age: int
? ? first_name = 'John'
? ? last_name: NoneStr = None
? ? signup_ts: Optional[datetime] = None
? ? list_of_ints: List[int]
m = Model(age=42, list_of_ints=[1, '2', b'3'])
print(m.middle_name) ?# not a model field!
Model() ?# will raise a validation error for age and list_of_ints

[mypy]
plugins = pydantic.mypy

[mypy]
plugins = pydantic.mypy
follow_imports = silent
warn_redundant_casts = True
warn_unused_ignores = True
disallow_any_generics = True
check_untyped_defs = True
no_implicit_reexport = True
# for strict mypy: (this is the tricky one :-))
disallow_untyped_defs = True
[pydantic-mypy]
init_forbid_extra = True
init_typed = True
warn_required_dynamic_aliases = True
warn_untyped_fields = True