mirror of https://github.com/Qiskit/qiskit.git
Hack in SimpleNamespace-like functionality to Options (#7347)
* Hack in SimpleNamespace-like functionality to Options This is an awful hack to support various SimpleNamespace-like operations that qiskit-dynamics are using. We need to transition downstream packages to the new Options API, but in the meantime, this makes the Options class behave as much like a SimpleNamespace as it can, while still keeping the new instance attributes and methods. * Suppress pylint bad assignment error I was surprised at how little pylint complained about the actual implementation, but it complains about the usage. This could conceivably be called a pylint bug; because we override `__setattr__`, pylint should perhaps recognise that general attribute setting might be allowed.
This commit is contained in:
Jake Lishman
GitHub
parent
ae55844b2b
commit
37684d48a7
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@ -26,12 +26,69 @@ class Options:
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options.
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"""
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_fields = {}
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# Here there are dragons.
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# This class preamble is an abhorrent hack to make `Options` work similarly to a
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# SimpleNamespace, but with its instance methods and attributes in a separate namespace. This
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# is required to make the initial release of Qiskit Terra 0.19 compatible with already released
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# versions of Qiskit Experiments, which rely on both of
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# options.my_key = my_value
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# transpile(qc, **options.__dict__)
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# working.
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#
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# Making `__dict__` a property which gets a slotted attribute solves the second line. The
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# slotted attributes are not stored in a `__dict__` anyway, and `__slots__` classes suppress the
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# creation of `__dict__`. That leaves it free for us to override it with a property, which
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# returns the options namespace `_fields`.
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#
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# We need to make attribute setting simply set options as well, to support statements of the
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# form `options.key = value`. We also need to ensure that existing uses do not override any new
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# methods. We do this by overriding `__setattr__` to purely write into our `_fields` dict
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# instead. This has the highly unusual behavior that
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# >>> options = Options()
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# >>> options.validator = "my validator option setting"
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# >>> options.validator
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# {}
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# >>> options.get("validator")
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# "my validator option setting"
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# This is the most we can do to support the old interface; _getting_ attributes must return the
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# new forms where appropriate, but setting will work with anything. All options can always be
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# returned by `Options.get`. To initialise the attributes in `__init__`, we need to dodge the
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# overriding of `__setattr__`, and upcall to `object.__setattr__`.
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#
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# To support copying and pickling, we also have to define how to set our state, because Python's
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# normal way of trying to get attributes in the unpickle will fail.
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#
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# This is a terrible hack, and is purely to ensure that Terra 0.19 does not break versions of
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# other Qiskit-family packages that are already deployed. It should be removed as soon as
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# possible.
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__slots__ = ("_fields", "validator")
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@property
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def __dict__(self):
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return self._fields
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def __setattr__(self, key, value):
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self._fields[key] = value
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def __getstate__(self):
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return (self._fields, self.validator)
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def __setstate__(self, state):
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_fields, validator = state
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super().__setattr__("_fields", _fields)
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super().__setattr__("validator", validator)
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def __init__(self, **kwargs):
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self._fields = {}
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self._fields.update(kwargs)
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self.validator = {}
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super().__setattr__("_fields", kwargs)
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super().__setattr__("validator", {})
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# The eldritch horrors are over, and normal service resumes below. Beware that while
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# `__setattr__` is overridden, you cannot do `self.x = y` (but `self.x[key] = y` is fine). This
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# should not be necessary, but if _absolutely_ required, you must do
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# super().__setattr__("x", y)
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# to avoid just setting a value in `_fields`.
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def __repr__(self):
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items = (f"{k}={v!r}" for k, v in self._fields.items())
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@ -121,14 +178,19 @@ class Options:
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self._fields.update(fields)
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def __getattr__(self, name):
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# This does not interrupt the normal lookup of things like methods or `_fields`, because
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# those are successfully resolved by the normal Python lookup apparatus. If we are here,
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# then lookup has failed, so we must be looking for an option. If the user has manually
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# called `self.__getattr__("_fields")` then they'll get the option not the full dict, but
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# that's not really our fault. `getattr(self, "_fields")` will still find the dict.
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try:
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return self._fields[name]
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except KeyError as ex:
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raise AttributeError(f"Attribute {name} is not defined") from ex
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raise AttributeError(f"Option {name} is not defined") from ex
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def get(self, field, default=None):
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"""Get an option value for a given key."""
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return getattr(self, field, default)
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return self._fields.get(field, default)
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def __str__(self):
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no_validator = super().__str__()
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@ -13,6 +13,9 @@
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# pylint: disable=missing-class-docstring,missing-function-docstring
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# pylint: disable=missing-module-docstring
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import copy
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import pickle
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from qiskit.providers import Options
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from qiskit.qobj.utils import MeasLevel
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@ -105,3 +108,87 @@ Where:
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options = Options(shots=1024)
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self.assertTrue(hasattr(options, "shots"))
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self.assertFalse(hasattr(options, "method"))
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class TestOptionsSimpleNamespaceBackwardCompatibility(QiskitTestCase):
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"""Tests that SimpleNamespace-like functionality that qiskit-experiments relies on for Options
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still works."""
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def test_unpacking_dict(self):
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kwargs = {"hello": "world", "a": "b"}
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options = Options(**kwargs)
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self.assertEqual(options.__dict__, kwargs)
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self.assertEqual({**options.__dict__}, kwargs)
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def test_setting_attributes(self):
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options = Options()
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options.hello = "world" # pylint: disable=assigning-non-slot
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options.a = "b" # pylint: disable=assigning-non-slot
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self.assertEqual(options.get("hello"), "world")
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self.assertEqual(options.get("a"), "b")
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self.assertEqual(options.__dict__, {"hello": "world", "a": "b"})
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def test_overriding_instance_attributes(self):
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"""Test that setting instance attributes and methods does not interfere with previously
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defined attributes and methods. This produces an inconsistency where
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>>> options = Options()
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>>> options.validators = "hello"
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>>> options.validators
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{}
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>>> options.get("validators")
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"hello"
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"""
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options = Options(get="a string")
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options.validator = "another string"
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setattr(options, "update_options", "not a method")
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options.update_options(_fields="not a dict")
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options.__dict__ = "also not a dict"
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self.assertEqual(
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options.__dict__,
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{
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"get": "a string",
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"validator": "another string",
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"update_options": "not a method",
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"_fields": "not a dict",
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"__dict__": "also not a dict",
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},
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)
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self.assertEqual(
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options._fields,
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{
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"get": "a string",
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"validator": "another string",
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"update_options": "not a method",
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"_fields": "not a dict",
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"__dict__": "also not a dict",
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},
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)
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self.assertEqual(options.validator, {})
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self.assertEqual(options.get("_fields"), "not a dict")
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def test_copy(self):
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options = Options(shots=1024, method="auto", meas_level=MeasLevel.KERNELED)
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options.set_validator("shots", (1, 1024))
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options.set_validator("method", ["auto", "statevector", "mps"])
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options.set_validator("meas_level", MeasLevel)
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expected = """Options(shots=1024, method='auto', meas_level=<MeasLevel.KERNELED: 1>)
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Where:
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\tshots is >= 1 and <= 1024
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\tmethod is one of ['auto', 'statevector', 'mps']
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\tmeas_level is of type <enum 'MeasLevel'>\n"""
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self.assertEqual(str(options), expected)
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self.assertEqual(str(copy.copy(options)), expected)
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def test_pickle(self):
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options = Options(shots=1024, method="auto", meas_level=MeasLevel.KERNELED)
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options.set_validator("shots", (1, 1024))
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options.set_validator("method", ["auto", "statevector", "mps"])
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options.set_validator("meas_level", MeasLevel)
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expected = """Options(shots=1024, method='auto', meas_level=<MeasLevel.KERNELED: 1>)
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Where:
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\tshots is >= 1 and <= 1024
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\tmethod is one of ['auto', 'statevector', 'mps']
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\tmeas_level is of type <enum 'MeasLevel'>\n"""
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self.assertEqual(str(options), expected)
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self.assertEqual(str(pickle.loads(pickle.dumps(options))), expected)
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