42 lines
1.2 KiB
Python
42 lines
1.2 KiB
Python
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# -*- coding: utf-8 -*-
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from __future__ import absolute_import, division, print_function
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class InstanceValidator(object):
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# We use a callable class to be able to change the ``__repr__``.
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def __init__(self, type_):
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self.type_ = type_
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def __call__(self, attr, value):
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if not isinstance(value, self.type_):
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raise TypeError(
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"'{name}' must be {type!r} (got {value!r} that is a "
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"{actual!r})."
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.format(name=attr.name, type=self.type_,
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actual=value.__class__, value=value),
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attr, self.type_, value,
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)
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def __repr__(self):
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return (
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"<instance_of validator for type {type!r}>"
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.format(type=self.type_)
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)
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def instance_of(type_):
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"""
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A validator that raises a :exc:`TypeError` if the initializer is called
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with a wrong type for this particular attribute (checks are perfomed using
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:func:`isinstance`).
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:param type_: The type to check for.
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:type type_: type
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The :exc:`TypeError` is raised with a human readable error message, the
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attribute (of type :class:`attr.Attribute`), the expected type and the
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value it got.
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"""
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return InstanceValidator(type_)
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