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python attrs中带有额外参数的自定义验证器

python-attrs python-3.x python

1

fasouto · 技术社区 · 7 年前

我有几个类是使用如下属性定义的:

from attr import attrs, attrib, validators

@attrs
class MyClass:
    name = attrib(])
    @name.validator
    def check_length(self, attribute, value):
        if not (3 <= len(value) <= 30):
            raise ValueError("Name must be between 3 and 30 characters")

    description = attrib()
    @description.validator
    def check_length(self, attribute, value):
        if not (10 <= len(value) <= 400):
            raise ValueError("Description must be between 10 and 400 characters")

对于一些属性,我需要创建一个验证器来检查数据是否在某个范围内。我想避免重复,所以我可以创建一个自定义验证器,在这里我为min和max传递一些额外的参数,如下所示:

def range_validator(instance, attribute, value, min_value, max_value):
    if  min_value >= len(value) >= max_value:
        raise ValueError("Must be between {} and {}".format(min_value, max_value))

但是我不知道如何从attrib()内部调用这个验证器来传递额外的参数(min_value和max_value),我的意思是这样做:

name = attrib(validator=[range_validator(self, 10, 30)])

1 回复 | 直到 7 年前

1

2

hynek 7 年前

你可以用 functools.partial :

def range_validator(instance, attribute, value, min_value, max_value):
    lv = len(value)
    if min_value > lv or lv > max_value:
        raise ValueError("Must be between {} and {}".format(min_value, max_value))

@attrs
class C:
    x = attrib(validator=partial(range_validator, min_value=10, max_value=30))

或者可以使用闭包:

def make_range_validator(min_value, max_value):
    def range_validator(instance, attribute, value):
        lv = len(value)
        if min_value > lv or lv > max_value:
            raise ValueError("Must be between {} and {}".format(min_value, max_value))

    return range_validator

@attrs
class C:
    x = attrib(validator=make_range_validator(10, 30))

(请注意,我冒昧地在验证器中修复了一个逻辑错误,您可能也想应用它。:))