Coverage for python/lsst/daf/butler/formatters/pickle.py: 68%

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26 statements  

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 

22from __future__ import annotations 

23 

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

25 

26__all__ = ("PickleFormatter", ) 

27 

28import pickle 

29 

30from typing import ( 

31 Any, 

32 Optional, 

33 Type, 

34) 

35 

36from .file import FileFormatter 

37 

38 

39class PickleFormatter(FileFormatter): 

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

41 files. 

42 """ 

43 extension = ".pickle" 

44 

45 unsupportedParameters = None 

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

47 

48 def _readFile(self, path: str, pytype: Optional[Type[Any]] = None) -> Any: 

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

50 

51 Parameters 

52 ---------- 

53 path : `str` 

54 Path to use to open the file. 

55 pytype : `class`, optional 

56 Not used by this implementation. 

57 

58 Returns 

59 ------- 

60 data : `object` 

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

62 if the file could not be opened. 

63 """ 

64 try: 

65 with open(path, "rb") as fd: 

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

67 except FileNotFoundError: 

68 data = None 

69 

70 return data 

71 

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

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

74 

75 Parameters 

76 ---------- 

77 inMemoryDataset : `object` 

78 Object to serialize. 

79 

80 Raises 

81 ------ 

82 Exception 

83 The file could not be written. 

84 """ 

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

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

87 

88 def _fromBytes(self, serializedDataset: bytes, pytype: Optional[Type[Any]] = None) -> Any: 

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

90 

91 Parameters 

92 ---------- 

93 serializedDataset : `bytes` 

94 Bytes object to unserialize. 

95 pytype : `class`, optional 

96 Not used by this implementation. 

97 

98 Returns 

99 ------- 

100 inMemoryDataset : `object` 

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

102 not be read. 

103 """ 

104 try: 

105 data = pickle.loads(serializedDataset) 

106 except pickle.PicklingError: 

107 data = None 

108 

109 return data 

110 

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

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

113 

114 Parameters 

115 ---------- 

116 inMemoryDataset : `object` 

117 Object to serialize 

118 

119 Returns 

120 ------- 

121 serializedDataset : `bytes` 

122 Bytes object representing the pickled object. 

123 

124 Raises 

125 ------ 

126 Exception 

127 The object could not be pickled. 

128 """ 

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