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

23""" 

24from __future__ import annotations 

25 

26__all__ = ("DeferredDatasetHandle",) 

27 

28import dataclasses 

29from typing import TYPE_CHECKING, Any 

30 

31if TYPE_CHECKING: 

32 from ._limited_butler import LimitedButler 

33 from .core import DataCoordinate, DatasetRef, StorageClass 

34 

35 

36@dataclasses.dataclass(frozen=True) 

37class DeferredDatasetHandle: 

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

39 

40 def get( 

41 self, 

42 *, 

43 component: str | None = None, 

44 parameters: dict | None = None, 

45 storageClass: str | StorageClass | None = None, 

46 ) -> Any: 

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

48 

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

50 parameters. 

51 

52 Parameters 

53 ---------- 

54 component : `str` or None 

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

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

57 parameters : `dict` or None 

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

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

60 be merged with the parameters dict used to construct the 

61 `DeferredDatasetHandle` class. 

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

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

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

65 the dataset type definition for this dataset or the storage 

66 class specified when this object was created. Specifying a 

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

68 This type must be compatible with the original type. 

69 

70 Returns 

71 ------- 

72 return : `Object` 

73 The dataset pointed to by this handle 

74 """ 

75 if self.parameters is not None: 

76 mergedParameters = self.parameters.copy() 

77 if parameters is not None: 

78 mergedParameters.update(parameters) 

79 elif parameters is not None: 

80 mergedParameters = parameters 

81 else: 

82 mergedParameters = {} 

83 if storageClass is None: 

84 storageClass = self.storageClass 

85 

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

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

88 

89 @property 

90 def dataId(self) -> DataCoordinate: 

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

92 (`DataCoordinate`). 

93 

94 Guaranteed to contain records. 

95 """ 

96 return self.ref.dataId 

97 

98 butler: LimitedButler 

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

100 """ 

101 

102 ref: DatasetRef 

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

104 """ 

105 

106 parameters: dict | None 

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

108 to be loaded (`dict` or `None`). 

109 """ 

110 

111 storageClass: str | StorageClass | None = None 

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