Validating data

Some types on middle can be validated based on single or multiple keywords that can be available to the field method, but will only trigger validation based on the type of the field.

Tip

Validation on middle is based on rules declared in the OpenAPI specification, so most of them should not be strange to those familiar with web development.

Important

All types have at least one validator: asserting if the type of the value is the one defined in the class (or None, if typing.Optional or have the keyword default set to None).

Warning

All validators that corresponds to a certain type will be called. This behavior may change in the future because I simply don’t know if, in the OpenAPI specification, one (certain validator) may exclude another.

Range validators

There are some validators that works within a certain range that may contains a max and a min value (with keywords specific for a type). Given these values are mostly quantitatives, they cannot be negative (or ValueError will be raised), except for instances of type int or float; nor the upper bound value can be equal or less than the lower bound value. Some other keywords may have some effect on these values as well.

\[lower\_bound \lt value \lt upper\_bound\]

Important

Optionally range validators can also be used only with the lower_bound or upper_bound value if no bound is needed in one of the values.

String validators

There are some validators for the str type that can

Range: min_length and max_length

\[min\_length \leqslant len(value) \leqslant max\_length\]

Setting min_length keyword to an integer would require that the input value should have at least the given value of length:

>>> import middle

>>> class TestModel(middle.Model):
...     name = middle.field(type=str, min_length=3)

>>> TestModel(name="hello")
TestModel(name='hello')

>>> TestModel(name="hi")

Given the input value above, here’s the resulting Traceback:

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 80, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init 70f3aaa3ccac019c22d47311619cd3804d1a9311>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 11, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 21, in min_str_len
    attribute.name, meta_value
middle.exceptions.ValidationError: 'name' must have a minimum length of 3 chars

Setting the max_length keyword to an integer would require that the input value should have no more than the given value of length:

>>> import middle

>>> class TestModel(middle.Model):
...     name: str = middle.field(max_length=5)

>>> TestModel(name="hello")
TestModel(name='hello')

>>> TestModel(name="hello, world")

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 80, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init 9b3b7c0ce74ad8f645d202b99d5df010c034e2b0>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 11, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 31, in max_str_len
    attribute.name, meta_value
middle.exceptions.ValidationError: 'name' must have a maximum length of 5 chars

pattern

Setting the pattern keyword to a string representing a regular expression (or a regular expression object) would require that the input value should match the value given:

>>> import middle

>>> class TestModel(middle.Model):
...     serial = {"type": str, "pattern": "^[0-9]+$"}

>>> TestModel(serial="123456")
TestModel(serial='123456')

>>> TestModel(serial="hello")

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 80, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init c36746f22b6ca0b15b44dff2665d92e7478d9031>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 11, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 41, in str_pattern
    attribute.name, meta_value
middle.exceptions.ValidationError: 'serial' did not match the given pattern: '^[0-9]+$'

format

To be developed.

Number validators

Range: minimum and maximum

\[minimum \leqslant value \leqslant maximum\]

Setting minimum keyword to an integer or float would require that the input value should have at least the required minimum value:

>>> import middle

>>> class TestModel(middle.Model):
...     value = {"type": int, "minimum": 5}

>>> TestModel(value=5)
TestModel(value=5)

>>> TestModel(value=20)
TestModel(value=20)

>>> TestModel(value=4)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init 6ed99d543406ed37c7405962f27f473476610ca9>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 60, in min_num_value
    attribute.name, meta_value
middle.exceptions.ValidationError: 'value' must have a minimum value of 5

Setting the maximum keyword to an integer or float would require that the input value shoud have no more than the maximum value:

>>> import middle

>>> class TestModel(middle.Model):
...     value: float = middle.field(maximum=3.14)

>>> TestModel(value=-5.0)
TestModel(value=-5.0)

>>> TestModel(value=3.141)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init 9fda1659ea481e0eb60414e362b3bd445d031dd3>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 79, in max_num_value
    attribute.name, meta_value
middle.exceptions.ValidationError: 'value' must have a maximum value of 3.14

exclusive_minimum

\[minimum \lt value\]

The exclusive_minimum keyword, being True, would exclude the minimum value from the validation:

>>> import middle

>>> class TestModel(middle.Model):
...     value = {"type": int, "minimum": 5, "exclusive_minimum": True}

>>> TestModel(value=6)
TestModel(value=6)

>>> TestModel(value=5)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init 29f97f0418f12486a7312929799ce2293fc24900>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 53, in min_num_value
    attribute.name, meta_value
middle.exceptions.ValidationError: 'value' must have a (exclusive) minimum value of 5

exclusive_maximum

\[value \lt maximum\]

The exclusive_maximum keyword, being True, would exclude the maximum value from the validation:

>>> import middle

>>> class TestModel(middle.Model):
...     value: float = middle.field(maximum=3.14, exclusive_maximum=True)

>>> TestModel(value=3.1)
TestModel(value=3.1)

>>> TestModel(value=3.14)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init 08e8fcc18b83475440f4c0239321aa61610c38b9>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 72, in max_num_value
    attribute.name, meta_value
middle.exceptions.ValidationError: 'value' must have a (exclusive) maximum value of 3.14

multiple_of

\[value {\rm\ mod\ }multiple\_of = 0\]

The multiple_of keyword specifies the multiple value that a value must have in order to have no remainder in a division operation. It works with int and float as well.

>>> import middle

>>> class TestModel(middle.Model):
...     value = {"type": int, "multiple_of": 3}

>>> TestModel(value=21)
TestModel(value=21)

>>> TestModel(value=22)

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init c24a18c0830f91f6079d00bbafff7e05f204e5a4>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 96, in num_multiple_of
    "'{}' must be multiple of {}".format(attribute.name, meta_value)
middle.exceptions.ValidationError: 'value' must be multiple of 3

List and Set validators

Range: min_items and max_items

\[min\_items \leqslant len(value) \leqslant max\_items\]

Setting min_items keyword to a List or Set would require that the input value should have at least the required number of items:

>>> import middle

>>> class TestModel(middle.Model):
...     value = {"type": List[int], "min_items": 3}

>>> TestModel(value=[1, 2, 3, 4])
TestModel(value=[1, 2, 3, 4])

>>> TestModel(value=[1, 2])

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init e1f1466567f03e1497438574116bf161e9400995>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 104, in list_min_items
    "'{}' has no enough items of {}".format(attribute.name, meta_value)
middle.exceptions.ValidationError: 'value' has no enough items of 3

Setting the max_items keyword to a List or Set would require that the input value shoud have no more than the required number of items:

>>> import middle

>>> class TestModel(middle.Model):
...     value: List[int] = middle.field(max_items=5)

>>> TestModel(value=[1, 2, 3, 4])
TestModel(value=[1, 2, 3, 4])

>>> TestModel(value=[1, 2, 3, 4, 5, 6])

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init 5180f70ad2fab18f88a0d4d0079cfcf36c2eb02a>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 113, in list_max_items
    attribute.name, meta_value
middle.exceptions.ValidationError: 'value' has more items than the limit of 5

unique_items

The unique_items keyword specifies that all values in the input value should be unique.

>>> import middle

>>> class TestModel(middle.Model):
...     value: List[int] = middle.field(unique_items=True)

>>> TestModel(value=[1, 2, 3, 4])
TestModel(value=[1, 2, 3, 4])

>>> TestModel(value=[1, 2, 3, 2])

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init 1687613eb0214900b54beb0d1c7a7831de866678>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 126, in list_unique_items
    "'{}' must only have unique items".format(attribute.name)
middle.exceptions.ValidationError: 'value' must only have unique items

Important

Remember that, to be unique, one value should be comparable with another. If you are comparing instances of models created with middle, please take a look on some tips regarding attrs.

Dict validators

Range: min_properties and max_properties

\[min\_properties \leqslant len(value) \leqslant max\_properties\]

Setting min_properties keyword to a Dict would require that the input value should have at least the required number of keys and values:

>>> import middle

>>> class TestModel(middle.Model):
...     value = {"type": Dict[str, int], "min_properties": 2}

>>> TestModel(value={"hello": 1, "world": 2})
TestModel(value={'hello': 1, 'world': 2})

>>> TestModel(value={"foo": 99})

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init 95407a54d787ed82415f9e4fc5762a3d1642f501>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 136, in dict_min_properties
    attribute.name, meta_value
middle.exceptions.ValidationError: 'value' has no enough properties of 2

Setting the max_properties keyword to a Dict would require that the input value shoud have no more than the required number of keys and values:

>>> import middle

>>> class TestModel(middle.Model):
...     value: Dict[str, int] = middle.field(max_properties=3)

>>> TestModel(value={"hello": 1, "world": 2})
TestModel(value={'hello': 1, 'world': 2})

>>> TestModel(value={"hello": 1, "world": 2, "foo": 3, "bar": 4})

Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "/home/dev/middle/src/middle/model.py", line 105, in __call__
    return super().__call__(**kwargs)
File "<attrs generated init dc8195b57024445a6dc3a09749cde9f62b46333d>", line 4, in __init__
File "/home/dev/.pyenv/versions/middle-3.6.6/lib/python3.6/site-packages/attr/_make.py", line 1668, in __call__
    v(inst, attr, value)
File "/home/dev/middle/src/middle/validators/common.py", line 10, in wrapper
    return func(meta_value, instance, attribute, value)
File "/home/dev/middle/src/middle/validators/common.py", line 147, in dict_max_properties
    attribute.name, meta_value
middle.exceptions.ValidationError: 'value' has more properties than the limit of 3