Coverage for python/lsst/daf/butler/_deferredDatasetHandle.py: 93%
34 statements
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1# This file is part of daf_butler.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (http://www.lsst.org).
6# See the COPYRIGHT file at the top-level directory of this distribution
7# for details of code ownership.
8#
9# This software is dual licensed under the GNU General Public License and also
10# under a 3-clause BSD license. Recipients may choose which of these licenses
11# to use; please see the files gpl-3.0.txt and/or bsd_license.txt,
12# respectively. If you choose the GPL option then the following text applies
13# (but note that there is still no warranty even if you opt for BSD instead):
14#
15# This program is free software: you can redistribute it and/or modify
16# it under the terms of the GNU General Public License as published by
17# the Free Software Foundation, either version 3 of the License, or
18# (at your option) any later version.
19#
20# This program is distributed in the hope that it will be useful,
21# but WITHOUT ANY WARRANTY; without even the implied warranty of
22# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
23# GNU General Public License for more details.
24#
25# You should have received a copy of the GNU General Public License
26# along with this program. If not, see <http://www.gnu.org/licenses/>.
28"""Module containing classes used with deferring dataset loading."""
30from __future__ import annotations
32__all__ = ("DeferredDatasetHandle",)
34import dataclasses
35from typing import TYPE_CHECKING, Any
37if TYPE_CHECKING:
38 from ._dataset_ref import DatasetRef
39 from ._limited_butler import LimitedButler
40 from ._storage_class import StorageClass
41 from .dimensions import DataCoordinate
44@dataclasses.dataclass(frozen=True)
45class DeferredDatasetHandle:
46 """Proxy class that provides deferred loading of datasets from a butler."""
48 def get(
49 self,
50 *,
51 component: str | None = None,
52 parameters: dict | None = None,
53 storageClass: str | StorageClass | None = None,
54 ) -> Any:
55 """Retrieve the dataset pointed to by this handle.
57 This handle may be used multiple times, possibly with different
58 parameters.
60 Parameters
61 ----------
62 component : `str` or None
63 If the deferred object is a component dataset type, this parameter
64 may specify the name of the component to use in the get operation.
65 The component is looked up in the storage class given when this
66 object was created, if there was one, and not in the storage class
67 the dataset was written with.
68 parameters : `dict` or None
69 The parameters argument will be passed to the butler get method.
70 It defaults to None. If the value is not None, this dict will
71 be merged with the parameters dict used to construct the
72 `DeferredDatasetHandle` class.
73 storageClass : `StorageClass` or `str`, optional
74 The storage class to be used to override the Python type
75 returned by this method. By default the returned type matches
76 the dataset type definition for this dataset or the storage
77 class specified when this object was created. Specifying a
78 read `StorageClass` can force a different type to be returned.
79 This type must be compatible with the original type. If
80 ``component`` is given this overrides the type of the component
81 rather than that of the composite.
83 Returns
84 -------
85 return : `Object`
86 The dataset pointed to by this handle.
87 """
88 if self.parameters is not None:
89 mergedParameters = self.parameters.copy()
90 if parameters is not None: 90 ↛ 91line 90 didn't jump to line 91 because the condition on line 90 was never true
91 mergedParameters.update(parameters)
92 elif parameters is not None:
93 mergedParameters = parameters
94 else:
95 mergedParameters = {}
97 if component is None:
98 # No component so apply the storage class override that was either
99 # given explicitly or provided to the constructor.
100 if storageClass is None:
101 storageClass = self.storageClass
102 return self.butler.get(self.ref, parameters=mergedParameters, storageClass=storageClass)
104 # We have a component request.
105 # The instance storageClass refers to the composite and so should
106 # not be applied to the component. If set we apply it to the
107 # requested ref before looking for components.
108 ref = self.ref
109 if self.storageClass is not None:
110 ref = ref.overrideStorageClass(self.storageClass)
112 # Now the component request goes through the overridden composite.
113 ref = ref.makeComponentRef(component)
115 # And run get with the override storage class if given.
116 return self.butler.get(ref, parameters=mergedParameters, storageClass=storageClass)
118 @property
119 def dataId(self) -> DataCoordinate:
120 """The full data ID associated with the dataset
121 (`DataCoordinate`).
123 Guaranteed to contain records.
124 """
125 return self.ref.dataId
127 butler: LimitedButler
128 """The butler that will be used to fetch the dataset (`LimitedButler`).
129 """
131 ref: DatasetRef
132 """Reference to the dataset (`DatasetRef`).
133 """
135 parameters: dict | None
136 """Optional parameters that may be used to specify a subset of the dataset
137 to be loaded (`dict` or `None`).
138 """
140 storageClass: str | StorageClass | None = None
141 """Optional storage class override that can be applied on ``get()``."""