Coverage for python/lsst/daf/butler/formatters/json.py: 82%
32 statements
« prev ^ index » next coverage.py v6.5.0, created at 2023-01-19 02:06 -0800
« prev ^ index » next coverage.py v6.5.0, created at 2023-01-19 02:06 -0800
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/>.
22from __future__ import annotations
24__all__ = ("JsonFormatter",)
26import dataclasses
27import json
28from typing import Any, Optional, Type
30from .file import FileFormatter
33class JsonFormatter(FileFormatter):
34 """Formatter implementation for JSON files."""
36 extension = ".json"
38 unsupportedParameters = None
39 """This formatter does not support any parameters (`frozenset`)"""
41 def _readFile(self, path: str, pytype: Optional[Type[Any]] = None) -> Any:
42 """Read a file from the path in JSON format.
44 Parameters
45 ----------
46 path : `str`
47 Path to use to open JSON format file.
48 pytype : `class`, optional
49 Not used by this implementation.
51 Returns
52 -------
53 data : `object`
54 Data as Python object read from JSON file.
55 """
56 with open(path, "rb") as fd:
57 data = self._fromBytes(fd.read(), pytype)
59 return data
61 def _writeFile(self, inMemoryDataset: Any) -> None:
62 """Write the in memory dataset to file on disk.
64 Will look for `_asdict()` method to aid JSON serialization, following
65 the approach of the simplejson module.
67 Parameters
68 ----------
69 inMemoryDataset : `object`
70 Object to serialize.
72 Raises
73 ------
74 Exception
75 The file could not be written.
76 """
77 self.fileDescriptor.location.uri.write(self._toBytes(inMemoryDataset))
79 def _fromBytes(self, serializedDataset: bytes, pytype: Optional[Type[Any]] = None) -> Any:
80 """Read the bytes object as a python object.
82 Parameters
83 ----------
84 serializedDataset : `bytes`
85 Bytes object to unserialize.
86 pytype : `class`, optional
87 Not used by this implementation.
89 Returns
90 -------
91 inMemoryDataset : `object`
92 The requested data as a Python object or None if the string could
93 not be read.
94 """
95 try:
96 data = json.loads(serializedDataset)
97 except json.JSONDecodeError:
98 data = None
100 return data
102 def _toBytes(self, inMemoryDataset: Any) -> bytes:
103 """Write the in memory dataset to a bytestring.
105 Parameters
106 ----------
107 inMemoryDataset : `object`
108 Object to serialize
110 Returns
111 -------
112 serializedDataset : `bytes`
113 bytes representing the serialized dataset.
115 Raises
116 ------
117 Exception
118 The object could not be serialized.
119 """
120 # For example, Pydantic models have a .json method so use it.
121 try:
122 return inMemoryDataset.json().encode()
123 except AttributeError:
124 pass
126 if dataclasses.is_dataclass(inMemoryDataset):
127 inMemoryDataset = dataclasses.asdict(inMemoryDataset)
128 elif hasattr(inMemoryDataset, "_asdict"):
129 inMemoryDataset = inMemoryDataset._asdict()
130 return json.dumps(inMemoryDataset, ensure_ascii=False).encode()