Coverage for python/lsst/daf/butler/_deferredDatasetHandle.py: 52%

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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/>. 

27 

28"""Module containing classes used with deferring dataset loading. 

29""" 

30from __future__ import annotations 

31 

32__all__ = ("DeferredDatasetHandle",) 

33 

34import dataclasses 

35from typing import TYPE_CHECKING, Any 

36 

37if TYPE_CHECKING: 

38 from ._limited_butler import LimitedButler 

39 from .core import DataCoordinate, DatasetRef, StorageClass 

40 

41 

42@dataclasses.dataclass(frozen=True) 

43class DeferredDatasetHandle: 

44 """Proxy class that provides deferred loading of datasets from a butler.""" 

45 

46 def get( 

47 self, 

48 *, 

49 component: str | None = None, 

50 parameters: dict | None = None, 

51 storageClass: str | StorageClass | None = None, 

52 ) -> Any: 

53 """Retrieve the dataset pointed to by this handle. 

54 

55 This handle may be used multiple times, possibly with different 

56 parameters. 

57 

58 Parameters 

59 ---------- 

60 component : `str` or None 

61 If the deferred object is a component dataset type, this parameter 

62 may specify the name of the component to use in the get operation. 

63 parameters : `dict` or None 

64 The parameters argument will be passed to the butler get method. 

65 It defaults to None. If the value is not None, this dict will 

66 be merged with the parameters dict used to construct the 

67 `DeferredDatasetHandle` class. 

68 storageClass : `StorageClass` or `str`, optional 

69 The storage class to be used to override the Python type 

70 returned by this method. By default the returned type matches 

71 the dataset type definition for this dataset or the storage 

72 class specified when this object was created. Specifying a 

73 read `StorageClass` can force a different type to be returned. 

74 This type must be compatible with the original type. 

75 

76 Returns 

77 ------- 

78 return : `Object` 

79 The dataset pointed to by this handle 

80 """ 

81 if self.parameters is not None: 

82 mergedParameters = self.parameters.copy() 

83 if parameters is not None: 

84 mergedParameters.update(parameters) 

85 elif parameters is not None: 

86 mergedParameters = parameters 

87 else: 

88 mergedParameters = {} 

89 if storageClass is None: 

90 storageClass = self.storageClass 

91 

92 ref = self.ref.makeComponentRef(component) if component is not None else self.ref 

93 return self.butler.get(ref, parameters=mergedParameters, storageClass=storageClass) 

94 

95 @property 

96 def dataId(self) -> DataCoordinate: 

97 """The full data ID associated with the dataset 

98 (`DataCoordinate`). 

99 

100 Guaranteed to contain records. 

101 """ 

102 return self.ref.dataId 

103 

104 butler: LimitedButler 

105 """The butler that will be used to fetch the dataset (`LimitedButler`). 

106 """ 

107 

108 ref: DatasetRef 

109 """Reference to the dataset (`DatasetRef`). 

110 """ 

111 

112 parameters: dict | None 

113 """Optional parameters that may be used to specify a subset of the dataset 

114 to be loaded (`dict` or `None`). 

115 """ 

116 

117 storageClass: str | StorageClass | None = None 

118 """Optional storage class override that can be applied on ``get()``."""