字段校验
自定义验证和对象之间的复杂关系可以使用 validator
装饰器来实现。
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)
"""
(这个脚本是完整的,它应该“按原样”运行)
关于验证器的一些注意事项:
- 验证器是“类方法”,因此它们收到的第一个参数值是
UserModel
类,而不是UserModel
的实例。 - 第二个参数始终是要验证的字段值; 它可以随意命名
- 您还可以将以下参数的任何子集添加到签名中(但名称必须匹配):
values
: 包含任何先前验证字段的名称到值映射的字典config
: 模型配置field
: 正在验证的字段。 对象的类型是pydantic.fields.ModelField
。**kwargs
: 如果提供,这将包括上面未在签名中明确列出的参数
- 验证器应该返回解析后的值或引发
ValueError
、TypeError
或AssertionError
(可以使用assert
语句)。
Warning
如果您使用 assert
语句,请记住使用 -O
优化标志 运行 Python 会禁用 assert
语句,验证器将停止工作。
-
在验证器依赖于其他值的地方,你应该知道:
- 验证时基于定义时的字段顺序.
例如。 在上面的示例中,
password2
可以访问password1
(和name
),但是password1
不能访问password2
。 有关字段如何排序的更多信息,请参阅 字段排序
- 如果在另一个字段上验证失败(或该字段丢失),它将不会包含在
values
中,比如在本例中的 “if 'password1' in values and ...”。
- 验证时基于定义时的字段顺序.
例如。 在上面的示例中,
前验证器和每项验证器(Pre and per-item validators)¶
验证器可以做一些更复杂的事情:
from typing import List
from pydantic import BaseModel, ValidationError, validator
class DemoModel(BaseModel):
square_numbers: List[int] = []
cube_numbers: List[int] = []
# '*' is the same as 'cube_numbers', 'square_numbers' here:
@validator('*', pre=True)
def split_str(cls, v):
if isinstance(v, str):
return v.split('|')
return v
@validator('cube_numbers', 'square_numbers')
def check_sum(cls, v):
if sum(v) > 42:
raise ValueError('sum of numbers greater than 42')
return v
@validator('square_numbers', each_item=True)
def check_squares(cls, v):
assert v ** 0.5 % 1 == 0, f'{v} is not a square number'
return v
@validator('cube_numbers', each_item=True)
def check_cubes(cls, v):
# 64 ** (1 / 3) == 3.9999999999999996 (!)
# this is not a good way of checking cubes
assert v ** (1 / 3) % 1 == 0, f'{v} is not a cubed number'
return v
print(DemoModel(square_numbers=[1, 4, 9]))
#> square_numbers=[1, 4, 9] cube_numbers=[]
print(DemoModel(square_numbers='1|4|16'))
#> square_numbers=[1, 4, 16] cube_numbers=[]
print(DemoModel(square_numbers=[16], cube_numbers=[8, 27]))
#> square_numbers=[16] cube_numbers=[8, 27]
try:
DemoModel(square_numbers=[1, 4, 2])
except ValidationError as e:
print(e)
"""
1 validation error for DemoModel
square_numbers -> 2
2 is not a square number (type=assertion_error)
"""
try:
DemoModel(cube_numbers=[27, 27])
except ValidationError as e:
print(e)
"""
1 validation error for DemoModel
cube_numbers
sum of numbers greater than 42 (type=value_error)
"""
from pydantic import BaseModel, ValidationError, validator
class DemoModel(BaseModel):
square_numbers: list[int] = []
cube_numbers: list[int] = []
# '*' is the same as 'cube_numbers', 'square_numbers' here:
@validator('*', pre=True)
def split_str(cls, v):
if isinstance(v, str):
return v.split('|')
return v
@validator('cube_numbers', 'square_numbers')
def check_sum(cls, v):
if sum(v) > 42:
raise ValueError('sum of numbers greater than 42')
return v
@validator('square_numbers', each_item=True)
def check_squares(cls, v):
assert v ** 0.5 % 1 == 0, f'{v} is not a square number'
return v
@validator('cube_numbers', each_item=True)
def check_cubes(cls, v):
# 64 ** (1 / 3) == 3.9999999999999996 (!)
# this is not a good way of checking cubes
assert v ** (1 / 3) % 1 == 0, f'{v} is not a cubed number'
return v
print(DemoModel(square_numbers=[1, 4, 9]))
#> square_numbers=[1, 4, 9] cube_numbers=[]
print(DemoModel(square_numbers='1|4|16'))
#> square_numbers=[1, 4, 16] cube_numbers=[]
print(DemoModel(square_numbers=[16], cube_numbers=[8, 27]))
#> square_numbers=[16] cube_numbers=[8, 27]
try:
DemoModel(square_numbers=[1, 4, 2])
except ValidationError as e:
print(e)
"""
1 validation error for DemoModel
square_numbers -> 2
2 is not a square number (type=assertion_error)
"""
try:
DemoModel(cube_numbers=[27, 27])
except ValidationError as e:
print(e)
"""
1 validation error for DemoModel
cube_numbers
sum of numbers greater than 42 (type=value_error)
"""
(这个脚本是完整的,它应该“按原样”运行)
还有几点需要注意:
- 通过传递多个字段名称,单个验证器可以应用于多个字段
- 通过传递特殊值
“*”
,也可以在所有字段上调用单个验证器 - 关键字参数
pre
将导致验证器在其他验证之前被调用 - 传递
each_item=True
将导致验证器应用于单个值(例如List
、Dict
、Set
等),而不是整个对象
子类验证器和 each_item
(Subclass Validators and each_item
)¶
如果将验证器与引用父类上的List
类型字段的子类一起使用,则使用each_item=True
将导致验证器不运行; 相反,列表必须以编程方式迭代。
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, 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)
"""
(这个脚本是完整的,它应该“按原样”运行)
始终验证(Validate Always)¶
出于性能原因,默认情况下,当未提供值时,不会为字段调用验证器。
然而,在某些情况下,始终调用验证器可能是有用的或需要的,例如 设置动态默认值。
from datetime import datetime
from pydantic import BaseModel, validator
class DemoModel(BaseModel):
ts: datetime = None
@validator('ts', pre=True, always=True)
def set_ts_now(cls, v):
return v or datetime.now()
print(DemoModel())
#> ts=datetime.datetime(2023, 5, 8, 16, 38, 2, 661248)
print(DemoModel(ts='2017-11-08T14:00'))
#> ts=datetime.datetime(2017, 11, 8, 14, 0)
(这个脚本是完整的,它应该“按原样”运行)
您通常希望将它与 pre
一起使用,因为否则与 always=True
pydantic 会尝试验证默认的 None
,这会导致错误。
重用校验器(Reuse validators)¶
有时,您会希望在多个字段/模型上使用相同的验证器(例如,规范化一些输入数据)。 比较“naive”的写法是编写一个单独的函数,然后从多个装饰器中调用它。 显然,这需要大量重复和样板代码。 为了避免这种情况,allow_reuse
参数已添加到 v1.2 中的 pydantic.validator
(默认情况下为 False
):
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)
jane_doe = Producer(name='JaNe DOE')
john_doe = Consumer(name='joHN dOe')
assert jane_doe.name == 'Jane Doe'
assert john_doe.name == 'John Doe'
(这个脚本是完整的,它应该“按原样”运行)
很明显,重复已经减少,模型再次变得几乎是声明性的。
Tip
如果您有很多要验证的字段,定义一个帮助函数通常是有意义的,您可以使用它来避免一遍又一遍地设置 allow_reuse=True
。
根验证器(Root Validators)¶
还可以对整个模型的数据执行验证。
from pydantic import BaseModel, ValidationError, root_validator
class UserModel(BaseModel):
username: str
password1: str
password2: str
@root_validator(pre=True)
def check_card_number_omitted(cls, values):
assert 'card_number' not in values, 'card_number should not be included'
return values
@root_validator
def check_passwords_match(cls, values):
pw1, pw2 = values.get('password1'), values.get('password2')
if pw1 is not None and pw2 is not None and pw1 != pw2:
raise ValueError('passwords do not match')
return values
print(UserModel(username='scolvin', password1='zxcvbn', password2='zxcvbn'))
#> username='scolvin' password1='zxcvbn' password2='zxcvbn'
try:
UserModel(username='scolvin', password1='zxcvbn', password2='zxcvbn2')
except ValidationError as e:
print(e)
"""
1 validation error for UserModel
__root__
passwords do not match (type=value_error)
"""
try:
UserModel(
username='scolvin',
password1='zxcvbn',
password2='zxcvbn',
card_number='1234',
)
except ValidationError as e:
print(e)
"""
1 validation error for UserModel
__root__
card_number should not be included (type=assertion_error)
"""
(这个脚本是完整的,它应该“按原样”运行)
如果 pre=True
根验证器引发错误,则不会进行字段验证。 与字段验证器一样,即使先前的验证器失败,默认情况下也会调用“post”(即 pre=False
)根验证器; 可以通过为验证器设置 skip_on_failure=True
关键字参数来更改此行为。
values
参数将是一个字典,其中包含通过字段验证的值和适用的字段默认值。
字段检查(Field Checks)¶
在创建类时,会检查验证器以确认它们指定的字段确实存在于模型中。
然而,有时这是不可取的:例如 如果您定义一个验证器来验证继承模型上的字段。 在这种情况下,您应该在验证器上设置 check_fields=False
。
数据类验证器(Dataclass Validators)¶
验证器还可以与 pydantic 数据类一起使用。
from datetime import datetime
from pydantic import validator
from pydantic.dataclasses import dataclass
@dataclass
class DemoDataclass:
ts: datetime = None
@validator('ts', pre=True, always=True)
def set_ts_now(cls, v):
return v or datetime.now()
print(DemoDataclass())
#> DemoDataclass(ts=datetime.datetime(2023, 5, 8, 16, 38, 2, 669536))
print(DemoDataclass(ts='2017-11-08T14:00'))
#> DemoDataclass(ts=datetime.datetime(2017, 11, 8, 14, 0))
(这个脚本是完整的,它应该“按原样”运行)