Coverage for python/lsst/daf/butler/formatters/pickle.py: 84%

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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"""Formatter associated with Python pickled objects.""" 

29 

30from __future__ import annotations 

31 

32__all__ = ("PickleFormatter",) 

33 

34import pickle 

35from typing import Any 

36 

37from .file import FileFormatter 

38 

39 

40class PickleFormatter(FileFormatter): 

41 """Interface for reading and writing Python objects to and from pickle 

42 files. 

43 """ 

44 

45 extension = ".pickle" 

46 

47 unsupportedParameters = None 

48 """This formatter does not support any parameters""" 

49 

50 def _readFile(self, path: str, pytype: type[Any] | None = None) -> Any: 

51 """Read a file from the path in pickle format. 

52 

53 Parameters 

54 ---------- 

55 path : `str` 

56 Path to use to open the file. 

57 pytype : `class`, optional 

58 Not used by this implementation. 

59 

60 Returns 

61 ------- 

62 data : `object` 

63 Either data as Python object read from the pickle file, or None 

64 if the file could not be opened. 

65 """ 

66 try: 

67 with open(path, "rb") as fd: 

68 data = self._fromBytes(fd.read(), pytype) 

69 except FileNotFoundError: 

70 data = None 

71 

72 return data 

73 

74 def _writeFile(self, inMemoryDataset: Any) -> None: 

75 """Write the in memory dataset to file on disk. 

76 

77 Parameters 

78 ---------- 

79 inMemoryDataset : `object` 

80 Object to serialize. 

81 

82 Raises 

83 ------ 

84 Exception 

85 The file could not be written. 

86 """ 

87 with open(self.fileDescriptor.location.path, "wb") as fd: 

88 pickle.dump(inMemoryDataset, fd, protocol=-1) 

89 

90 def _fromBytes(self, serializedDataset: bytes, pytype: type[Any] | None = None) -> Any: 

91 """Read the bytes object as a python object. 

92 

93 Parameters 

94 ---------- 

95 serializedDataset : `bytes` 

96 Bytes object to unserialize. 

97 pytype : `class`, optional 

98 Not used by this implementation. 

99 

100 Returns 

101 ------- 

102 inMemoryDataset : `object` 

103 The requested data as a object, or None if the string could 

104 not be read. 

105 """ 

106 try: 

107 data = pickle.loads(serializedDataset) 

108 except pickle.PicklingError: 

109 data = None 

110 

111 return data 

112 

113 def _toBytes(self, inMemoryDataset: Any) -> bytes: 

114 """Write the in memory dataset to a bytestring. 

115 

116 Parameters 

117 ---------- 

118 inMemoryDataset : `object` 

119 Object to serialize 

120 

121 Returns 

122 ------- 

123 serializedDataset : `bytes` 

124 Bytes object representing the pickled object. 

125 

126 Raises 

127 ------ 

128 Exception 

129 The object could not be pickled. 

130 """ 

131 return pickle.dumps(inMemoryDataset, protocol=-1)