Viewing file:  validators.py (3.3 KB) -rw-r--r--
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"""
Commonly useful validators.
"""
from __future__ import absolute_import, division, print_function
from ._make import attr, attributes
@attributes(repr=False)
class _InstanceOfValidator(object):
type = attr()
def __call__(self, inst, attr, value):
"""
We use a callable class to be able to change the ``__repr__``.
"""
if not isinstance(value, self.type):
raise TypeError(
"'{name}' must be {type!r} (got {value!r} that is a "
"{actual!r})."
.format(name=attr.name, type=self.type,
actual=value.__class__, value=value),
attr, self.type, value,
)
def __repr__(self):
return (
"<instance_of validator for type {type!r}>"
.format(type=self.type)
)
def instance_of(type):
"""
A validator that raises a :exc:`TypeError` if the initializer is called
with a wrong type for this particular attribute (checks are perfomed using
:func:`isinstance`).
:param type: The type to check for.
:type type: type
The :exc:`TypeError` is raised with a human readable error message, the
attribute (of type :class:`attr.Attribute`), the expected type and the
value it got.
"""
return _InstanceOfValidator(type)
@attributes(repr=False)
class _ProvidesValidator(object):
interface = attr()
def __call__(self, inst, attr, value):
"""
We use a callable class to be able to change the ``__repr__``.
"""
if not self.interface.providedBy(value):
raise TypeError(
"'{name}' must provide {interface!r} which {value!r} "
"doesn't."
.format(name=attr.name, interface=self.interface, value=value),
attr, self.interface, value,
)
def __repr__(self):
return (
"<provides validator for interface {interface!r}>"
.format(interface=self.interface)
)
def provides(interface):
"""
A validator that raises a :exc:`TypeError` if the initializer is called
with an object that does not provide the requested *interface* (checks are
performed using ``interface.providedBy(value)`` (see `zope.interface
<http://docs.zope.org/zope.interface/>`_).
:param interface: The interface to check for.
:type interface: zope.interface.Interface
The :exc:`TypeError` is raised with a human readable error message, the
attribute (of type :class:`attr.Attribute`), the expected interface, and
the value it got.
"""
return _ProvidesValidator(interface)
@attributes(repr=False)
class _OptionalValidator(object):
validator = attr()
def __call__(self, inst, attr, value):
if value is None:
return
return self.validator(inst, attr, value)
def __repr__(self):
return (
"<optional validator for {type} or None>"
.format(type=repr(self.validator))
)
def optional(validator):
"""
A validator that makes an attribute optional. An optional attribute is one
which can be set to ``None`` in addition to satisfying the requirements of
the sub-validator.
:param validator: A validator that is used for non-``None`` values.
"""
return _OptionalValidator(validator)
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