Coverage for python/lsst/daf/butler/formatters/yaml.py : 31%

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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 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__ = ("YamlFormatter", )
26import builtins
27import yaml
29from typing import (
30 TYPE_CHECKING,
31 Any,
32 Optional,
33 Type,
34)
36from .file import FileFormatter
38if TYPE_CHECKING: 38 ↛ 39line 38 didn't jump to line 39, because the condition on line 38 was never true
39 from lsst.daf.butler import StorageClass
42class YamlFormatter(FileFormatter):
43 """Interface for reading and writing Python objects to and from YAML files.
44 """
45 extension = ".yaml"
47 unsupportedParameters = None
48 """This formatter does not support any parameters"""
50 def _readFile(self, path: str, pytype: Type[Any] = None) -> Any:
51 """Read a file from the path in YAML format.
53 Parameters
54 ----------
55 path : `str`
56 Path to use to open YAML format file.
57 pytype : `class`, optional
58 Not used by this implementation.
60 Returns
61 -------
62 data : `object`
63 Either data as Python object read from YAML file, or None
64 if the file could not be opened.
66 Notes
67 -----
68 The `~yaml.UnsafeLoader` is used when parsing the YAML file.
69 """
70 try:
71 with open(path, "rb") as fd:
72 data = self._fromBytes(fd.read(), pytype)
73 except FileNotFoundError:
74 data = None
76 return data
78 def _fromBytes(self, serializedDataset: bytes, pytype: Optional[Type[Any]] = None) -> Any:
79 """Read the bytes object as a python object.
81 Parameters
82 ----------
83 serializedDataset : `bytes`
84 Bytes object to unserialize.
85 pytype : `class`, optional
86 Not used by this implementation.
88 Returns
89 -------
90 inMemoryDataset : `object`
91 The requested data as an object, or None if the string could
92 not be read.
93 """
94 try:
95 data = yaml.load(serializedDataset, Loader=yaml.FullLoader)
96 except yaml.YAMLError:
97 data = None
98 try:
99 data = data.exportAsDict()
100 except AttributeError:
101 pass
102 return data
104 def _writeFile(self, inMemoryDataset: Any) -> None:
105 """Write the in memory dataset to file on disk.
107 Will look for `_asdict()` method to aid YAML serialization, following
108 the approach of the simplejson module.
110 Parameters
111 ----------
112 inMemoryDataset : `object`
113 Object to serialize.
115 Raises
116 ------
117 Exception
118 The file could not be written.
119 """
120 with open(self.fileDescriptor.location.path, "wb") as fd:
121 if hasattr(inMemoryDataset, "_asdict"):
122 inMemoryDataset = inMemoryDataset._asdict()
123 fd.write(self._toBytes(inMemoryDataset))
125 def _toBytes(self, inMemoryDataset: Any) -> bytes:
126 """Write the in memory dataset to a bytestring.
128 Parameters
129 ----------
130 inMemoryDataset : `object`
131 Object to serialize
133 Returns
134 -------
135 serializedDataset : `bytes`
136 YAML string encoded to bytes.
138 Raises
139 ------
140 Exception
141 The object could not be serialized.
142 """
143 return yaml.dump(inMemoryDataset).encode()
145 def _coerceType(self, inMemoryDataset: Any, storageClass: StorageClass,
146 pytype: Optional[Type[Any]] = None) -> Any:
147 """Coerce the supplied inMemoryDataset to type `pytype`.
149 Parameters
150 ----------
151 inMemoryDataset : `object`
152 Object to coerce to expected type.
153 storageClass : `StorageClass`
154 StorageClass associated with `inMemoryDataset`.
155 pytype : `type`, optional
156 Override type to use for conversion.
158 Returns
159 -------
160 inMemoryDataset : `object`
161 Object of expected type `pytype`.
162 """
163 if pytype is not None and not hasattr(builtins, pytype.__name__):
164 if storageClass.isComposite():
165 inMemoryDataset = storageClass.assembler().assemble(inMemoryDataset, pytype=pytype)
166 elif not isinstance(inMemoryDataset, pytype):
167 # Hope that we can pass the arguments in directly
168 inMemoryDataset = pytype(inMemoryDataset)
169 return inMemoryDataset