lsst.obs.base  20.0.0-34-gdb4d86a+b43b2c05ff
pexConfig.py
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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
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13 #
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15 # but WITHOUT ANY WARRANTY; without even the implied warranty of
16 # MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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20 # along with this program. If not, see <http://www.gnu.org/licenses/>.
21 
22 from __future__ import annotations
23 
24 __all__ = ("PexConfigFormatter", )
25 
26 import os.path
27 
28 from typing import (
29  Any,
30  Optional,
31  Type,
32 )
33 
34 from lsst.utils import doImport
35 from lsst.daf.butler.formatters.file import FileFormatter
36 
37 
38 class PexConfigFormatter(FileFormatter):
39  """Interface for reading and writing pex.config.Config objects from disk.
40  """
41  extension = ".py"
42 
43  def _readFile(self, path: str, pytype: Optional[Type[Any]] = None) -> Any:
44  """Read a pex.config.Config instance from the given file.
45 
46  Parameters
47  ----------
48  path : `str`
49  Path to use to open the file.
50  pytype : `type`
51  Class to use to read the config file.
52 
53  Returns
54  -------
55  data : `lsst.pex.config.Config`
56  Instance of class ``pytype`` read from config file. `None`
57  if the file could not be opened.
58  """
59  if pytype is None:
60  raise RuntimeError("A python type is always required for reading pex_config Config files")
61 
62  if not os.path.exists(path):
63  return None
64  instance = pytype()
65  # Configs can only be loaded if you use the correct derived type,
66  # but we can't really store the correct derive type in the StorageClass
67  # because that'd be a huge proliferation of StorageClasses.
68  # Instead, we use a bit of a hack: try to load using the base-class
69  # Config, inspect the exception message to obtain the class we should
70  # have used, import that, and try it instead.
71  # TODO: clean this up, somehow.
72  try:
73  instance.load(path)
74  return instance
75  except AssertionError as err:
76  msg = str(err)
77  if not msg.startswith("config is of type"):
78  raise RuntimeError("Unexpected assertion; cannot infer Config class type.") from err
79  actualPyTypeStr = msg.split()[-1]
80  actualPyType = doImport(actualPyTypeStr)
81  instance = actualPyType()
82  instance.load(path)
83  return instance
84 
85  def _writeFile(self, inMemoryDataset: Any) -> None:
86  """Write the in memory dataset to file on disk.
87 
88  Parameters
89  ----------
90  inMemoryDataset : `object`
91  Object to serialize.
92 
93  Raises
94  ------
95  Exception
96  The file could not be written.
97  """
98  inMemoryDataset.save(self.fileDescriptor.location.path)
lsst::utils
lsst.obs.base.formatters.pexConfig.PexConfigFormatter
Definition: pexConfig.py:38