Coverage for python/lsst/daf/butler/formatters/json.py: 84%
33 statements
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« prev ^ index » next coverage.py v7.2.7, created at 2023-08-12 09:19 +0000
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 contextlib
27import dataclasses
28import json
29from typing import Any
31from .file import FileFormatter
34class JsonFormatter(FileFormatter):
35 """Formatter implementation for JSON files."""
37 extension = ".json"
39 unsupportedParameters = None
40 """This formatter does not support any parameters (`frozenset`)"""
42 def _readFile(self, path: str, pytype: type[Any] | None = None) -> Any:
43 """Read a file from the path in JSON format.
45 Parameters
46 ----------
47 path : `str`
48 Path to use to open JSON format file.
49 pytype : `class`, optional
50 Not used by this implementation.
52 Returns
53 -------
54 data : `object`
55 Data as Python object read from JSON file.
56 """
57 with open(path, "rb") as fd:
58 data = self._fromBytes(fd.read(), pytype)
60 return data
62 def _writeFile(self, inMemoryDataset: Any) -> None:
63 """Write the in memory dataset to file on disk.
65 Will look for `_asdict()` method to aid JSON serialization, following
66 the approach of the simplejson module.
68 Parameters
69 ----------
70 inMemoryDataset : `object`
71 Object to serialize.
73 Raises
74 ------
75 Exception
76 The file could not be written.
77 """
78 self.fileDescriptor.location.uri.write(self._toBytes(inMemoryDataset))
80 def _fromBytes(self, serializedDataset: bytes, pytype: type[Any] | None = None) -> Any:
81 """Read the bytes object as a python object.
83 Parameters
84 ----------
85 serializedDataset : `bytes`
86 Bytes object to unserialize.
87 pytype : `class`, optional
88 Not used by this implementation.
90 Returns
91 -------
92 inMemoryDataset : `object`
93 The requested data as a Python object or None if the string could
94 not be read.
95 """
96 try:
97 data = json.loads(serializedDataset)
98 except json.JSONDecodeError:
99 data = None
101 return data
103 def _toBytes(self, inMemoryDataset: Any) -> bytes:
104 """Write the in memory dataset to a bytestring.
106 Parameters
107 ----------
108 inMemoryDataset : `object`
109 Object to serialize
111 Returns
112 -------
113 serializedDataset : `bytes`
114 bytes representing the serialized dataset.
116 Raises
117 ------
118 Exception
119 The object could not be serialized.
120 """
121 # Try different standardized methods for native json.
122 # For example, Pydantic models have a .model_dump_json method.
123 # v1 models without compatibility layer will need .json()
124 with contextlib.suppress(AttributeError):
125 return inMemoryDataset.model_dump_json().encode()
126 with contextlib.suppress(AttributeError):
127 return inMemoryDataset.json().encode()
129 if dataclasses.is_dataclass(inMemoryDataset):
130 inMemoryDataset = dataclasses.asdict(inMemoryDataset)
131 elif hasattr(inMemoryDataset, "_asdict"):
132 inMemoryDataset = inMemoryDataset._asdict()
133 return json.dumps(inMemoryDataset, ensure_ascii=False).encode()