Hide keyboard shortcuts

Hot-keys on this page

r m x p   toggle line displays

j k   next/prev highlighted chunk

0   (zero) top of page

1   (one) first highlighted chunk

1

2

3

4

5

6

7

8

9

10

11

12

13

14

15

16

17

18

19

20

21

22

23

24

25

26

27

28

29

30

31

32

33

34

35

36

37

38

39

40

41

42

43

44

45

46

47

48

49

50

51

52

53

54

55

56

57

58

59

60

61

62

63

64

65

66

67

68

69

70

71

72

73

74

75

76

77

78

79

80

81

82

83

84

85

86

87

88

89

90

91

92

93

94

95

96

97

98

99

100

101

102

103

104

105

106

107

108

109

110

111

112

113

114

115

116

117

118

119

120

121

122

123

124

125

126

127

128

129

130

131

132

133

134

135

136

137

138

139

140

141

142

143

144

145

146

147

# This file is part of daf_butler. 

# 

# Developed for the LSST Data Management System. 

# This product includes software developed by the LSST Project 

# (http://www.lsst.org). 

# See the COPYRIGHT file at the top-level directory of this distribution 

# for details of code ownership. 

# 

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

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

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

# (at your option) any later version. 

# 

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

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

# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the 

# GNU General Public License for more details. 

# 

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

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

 

__all__ = ("JsonFormatter", ) 

 

import builtins 

import json 

 

from lsst.daf.butler.formatters.fileFormatter import FileFormatter 

 

 

class JsonFormatter(FileFormatter): 

"""Interface for reading and writing Python objects to and from JSON files. 

""" 

extension = ".json" 

 

unsupportedParameters = None 

"""This formatter does not support any parameters (`frozenset`)""" 

 

def _readFile(self, path, pytype=None): 

"""Read a file from the path in JSON format. 

 

Parameters 

---------- 

path : `str` 

Path to use to open JSON format file. 

 

Returns 

------- 

data : `object` 

Either data as Python object read from JSON file, or None 

if the file could not be opened. 

""" 

try: 

with open(path, "rb") as fd: 

data = self._fromBytes(fd.read()) 

except FileNotFoundError: 

data = None 

 

return data 

 

def _writeFile(self, inMemoryDataset): 

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

 

Will look for `_asdict()` method to aid JSON serialization, following 

the approach of the simplejson module. 

 

Parameters 

---------- 

inMemoryDataset : `object` 

Object to serialize. 

 

Raises 

------ 

Exception 

The file could not be written. 

""" 

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

if hasattr(inMemoryDataset, "_asdict"): 

inMemoryDataset = inMemoryDataset._asdict() 

fd.write(self._toBytes(inMemoryDataset)) 

 

def _fromBytes(self, serializedDataset, pytype=None): 

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

 

Parameters 

---------- 

serializedDataset : `bytes` 

Bytes object to unserialize. 

pytype : `class`, optional 

Not used by this implementation. 

 

Returns 

------- 

inMemoryDataset : `object` 

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

not be read. 

""" 

try: 

data = json.loads(serializedDataset) 

except json.JSONDecodeError: 

data = None 

 

return data 

 

def _toBytes(self, inMemoryDataset): 

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

 

Parameters 

---------- 

inMemoryDataset : `object` 

Object to serialize 

 

Returns 

------- 

serializedDataset : `bytes` 

bytes representing the serialized dataset. 

 

Raises 

------ 

Exception 

The object could not be serialized. 

""" 

return json.dumps(inMemoryDataset, ensure_ascii=False).encode() 

 

def _coerceType(self, inMemoryDataset, storageClass, pytype=None): 

"""Coerce the supplied inMemoryDataset to type `pytype`. 

 

Parameters 

---------- 

inMemoryDataset : `object` 

Object to coerce to expected type. 

storageClass : `StorageClass` 

StorageClass associated with `inMemoryDataset`. 

pytype : `type`, optional 

Override type to use for conversion. 

 

Returns 

------- 

inMemoryDataset : `object` 

Object of expected type `pytype`. 

""" 

if not hasattr(builtins, pytype.__name__): 

142 ↛ 144line 142 didn't jump to line 144, because the condition on line 142 was never false if storageClass.isComposite(): 

inMemoryDataset = storageClass.assembler().assemble(inMemoryDataset, pytype=pytype) 

elif not isinstance(inMemoryDataset, pytype): 

# Hope that we can pass the arguments in directly 

inMemoryDataset = pytype(inMemoryDataset) 

return inMemoryDataset