Coverage for python/lsst/afw/table/_source.py: 34%

19 statements  

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1# This file is part of afw. 

2# 

3# Developed for the LSST Data Management System. 

4# This product includes software developed by the LSST Project 

5# (https://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 <https://www.gnu.org/licenses/>. 

21 

22__all__ = [] 

23 

24from lsst.utils import continueClass 

25from ._base import Catalog 

26from ._table import SourceCatalog, SourceTable 

27 

28Catalog.register("Source", SourceCatalog) 

29 

30 

31@continueClass 

32class SourceCatalog: 

33 

34 def getChildren(self, parent, *args): 

35 """Return the subset of self for which the parent field equals the 

36 given value. 

37 

38 In order for this method to return the correct result, it must be 

39 sorted by parent (i.e. self.isSorted(SourceTable.getParentKey()) must 

40 be True). This is naturally the case with SourceCatalogs produced by 

41 the detection and deblending tasks, but it may not be true when 

42 concatenating multiple such catalogs. 

43 

44 Additional Catalogs or sequences whose elements correspond in order to 

45 the records of self (i.e. ``zip(self, *args)`` is valid) will be 

46 subset using the same slice object used on self, and these subsets 

47 will be returned along with the subset of self. 

48 

49 Parameters 

50 ---------- 

51 parent : `int` or `iterable` of `int` 

52 ID(s) of the parent(s) to get children for. 

53 args : `~lsst.afw.table.Catalog` 

54 Additional catalogs to subset for the children to return. 

55 

56 Returns 

57 ------- 

58 children : a single iterable of `~lsst.afw.table.SourceRecord` 

59 Children sources if ``parent`` is of type `int`, or a generator 

60 yielding a `~lsst.afw.table.SourceRecord`s Children sources for 

61 each parent if ``parent`` is an `iterable`. 

62 

63 Raises 

64 ------ 

65 AssertionError 

66 Raised if the catalog is not sorted by the parent key. 

67 

68 Notes 

69 ----- 

70 Each call to this function checks if the catalog is sorted, which is 

71 of O(n) complexity, while fetching the children is of O(log n). To 

72 minimize the computational overhead, it is preferable to prepare an 

73 iterable of parent ids for which the children need to be fetched and 

74 pass the iterable as ``parent``. 

75 """ 

76 if not self.isSorted(SourceTable.getParentKey()): 

77 raise AssertionError( 

78 "The table is not sorted by parent, so cannot getChildren") 

79 

80 def _getChildrenWithoutChecking(parent): 

81 """Return the subset of self for which the parent field equals the 

82 given value. 

83 

84 This function works as desired only if `self` is sorted by the 

85 parent key, but does not check if it is sorted. This function must 

86 be used only after ensuring outside of the function that 

87 self.isSorted(SourceTable.getParentKey() evaluates to True. 

88 

89 Parameter 

90 --------- 

91 parent : `int` 

92 ID of the parent to get children for. 

93 

94 Returns 

95 ------- 

96 children : iterable of `~lsst.afw.table.SourceRecord` 

97 Children sources. 

98 """ 

99 s = self.equal_range(parent, SourceTable.getParentKey()) 

100 if args: 

101 return (self[s],) + tuple(arg[s] for arg in args) 

102 else: 

103 return self[s] 

104 

105 try: 

106 return (_getChildrenWithoutChecking(p) for p in parent) 

107 except TypeError: 

108 return _getChildrenWithoutChecking(parent)