Coverage for python/lsst/daf/butler/_deferredDatasetHandle.py: 50%

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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 program is free software: you can redistribute it and/or modify 

10# it under the terms of the GNU General Public License as published by 

11# the Free Software Foundation, either version 3 of the License, or 

12# (at your option) any later version. 

13# 

14# This program is distributed in the hope that it will be useful, 

15# but WITHOUT ANY WARRANTY; without even the implied warranty of 

16# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

17# GNU General Public License for more details. 

18# 

19# You should have received a copy of the GNU General Public License 

20# along with this program. If not, see <http://www.gnu.org/licenses/>. 

21 

22""" 

23Module containing classes used with deferring dataset loading 

24""" 

25from __future__ import annotations 

26 

27__all__ = ("DeferredDatasetHandle",) 

28 

29import dataclasses 

30from typing import TYPE_CHECKING, Any, Optional, Union 

31 

32if TYPE_CHECKING: 

33 from ._limited_butler import LimitedButler 

34 from .core import DataCoordinate, DatasetRef, StorageClass 

35 

36 

37@dataclasses.dataclass(frozen=True) 

38class DeferredDatasetHandle: 

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

40 

41 def get( 

42 self, 

43 *, 

44 component: Optional[str] = None, 

45 parameters: Optional[dict] = None, 

46 storageClass: str | StorageClass | None = None, 

47 ) -> Any: 

48 """Retrieves the dataset pointed to by this handle 

49 

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

51 parameters. 

52 

53 Parameters 

54 ---------- 

55 component : `str` or None 

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

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

58 parameters : `dict` or None 

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

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

61 be merged with the parameters dict used to construct the 

62 `DeferredDatasetHandle` class. 

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

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

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

66 the dataset type definition for this dataset or the storage 

67 class specified when this object was created. Specifying a 

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

69 This type must be compatible with the original type. 

70 

71 Returns 

72 ------- 

73 return : `Object` 

74 The dataset pointed to by this handle 

75 """ 

76 if self.parameters is not None: 

77 mergedParameters = self.parameters.copy() 

78 if parameters is not None: 

79 mergedParameters.update(parameters) 

80 elif parameters is not None: 

81 mergedParameters = parameters 

82 else: 

83 mergedParameters = {} 

84 if storageClass is None: 

85 storageClass = self.storageClass 

86 

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

88 return self.butler.getDirect(ref, parameters=mergedParameters, storageClass=storageClass) 

89 

90 @property 

91 def dataId(self) -> DataCoordinate: 

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

93 (`DataCoordinate`). 

94 

95 Guaranteed to contain records. 

96 """ 

97 return self.ref.dataId 

98 

99 butler: LimitedButler 

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

101 """ 

102 

103 ref: DatasetRef 

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

105 """ 

106 

107 parameters: Optional[dict] 

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

109 to be loaded (`dict` or `None`). 

110 """ 

111 

112 storageClass: Optional[Union[str, StorageClass]] = None 

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