Coverage for python/lsst/daf/butler/_deferredDatasetHandle.py: 52%
30 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.
29"""
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 parameters : `dict` or None
66 The parameters argument will be passed to the butler get method.
67 It defaults to None. If the value is not None, this dict will
68 be merged with the parameters dict used to construct the
69 `DeferredDatasetHandle` class.
70 storageClass : `StorageClass` or `str`, optional
71 The storage class to be used to override the Python type
72 returned by this method. By default the returned type matches
73 the dataset type definition for this dataset or the storage
74 class specified when this object was created. Specifying a
75 read `StorageClass` can force a different type to be returned.
76 This type must be compatible with the original type.
78 Returns
79 -------
80 return : `Object`
81 The dataset pointed to by this handle.
82 """
83 if self.parameters is not None:
84 mergedParameters = self.parameters.copy()
85 if parameters is not None:
86 mergedParameters.update(parameters)
87 elif parameters is not None:
88 mergedParameters = parameters
89 else:
90 mergedParameters = {}
91 if storageClass is None:
92 storageClass = self.storageClass
94 ref = self.ref.makeComponentRef(component) if component is not None else self.ref
95 return self.butler.get(ref, parameters=mergedParameters, storageClass=storageClass)
97 @property
98 def dataId(self) -> DataCoordinate:
99 """The full data ID associated with the dataset
100 (`DataCoordinate`).
102 Guaranteed to contain records.
103 """
104 return self.ref.dataId
106 butler: LimitedButler
107 """The butler that will be used to fetch the dataset (`LimitedButler`).
108 """
110 ref: DatasetRef
111 """Reference to the dataset (`DatasetRef`).
112 """
114 parameters: dict | None
115 """Optional parameters that may be used to specify a subset of the dataset
116 to be loaded (`dict` or `None`).
117 """
119 storageClass: str | StorageClass | None = None
120 """Optional storage class override that can be applied on ``get()``."""