Coverage for python/lsst/obs/base/exposureIdInfo.py : 21%

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1# This file is part of obs_base.
2#
3# Developed for the LSST Data Management System.
4# This product includes software developed by the LSST Project
5# (https://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 <https://www.gnu.org/licenses/>.
22__all__ = ["ExposureIdInfo"]
25class ExposureIdInfo(object):
26 """Exposure ID and number of bits used.
28 Attributes include:
30 expId
31 exposure ID as an int
32 expBits
33 maximum number of bits allowed for exposure IDs
34 maxBits
35 maximum number of bits available for values that combine exposure ID
36 with other information, such as source ID
37 unusedBits
38 maximum number of bits available for non-exposure info
39 (maxBits - expBits)
41 One common use is creating an ID factory for making a source table.
42 For example, given a data butler `butler` and a data ID `dataId`:
44 .. code-block:: python
46 from lsst.afw.table import IdFactory, SourceTable
47 exposureIdInfo = butler.get("expIdInfo", dataId)
48 sourceIdFactory = IdFactory.makeSource(exposureIdInfo.expId,
49 exposureIdInfo.unusedBits)
50 schema = SourceTable.makeMinimalSchema()
51 #...add fields to schema as desired, then...
52 sourceTable = SourceTable.make(self.schema, sourceIdFactory)
54 At least one bit must be reserved, even if there is no exposure ID, for
55 reasons that are not entirely clear (this is DM-6664).
56 """
58 def __init__(self, expId=0, expBits=1, maxBits=64):
59 """Construct an ExposureIdInfo
61 See the class doc string for an explanation of the arguments.
62 """
63 expId = int(expId)
64 expBits = int(expBits)
65 maxBits = int(maxBits)
67 if expId.bit_length() > expBits:
68 raise RuntimeError("expId=%s uses %s bits > expBits=%s" % (expId, expId.bit_length(), expBits))
69 if maxBits < expBits:
70 raise RuntimeError("expBits=%s > maxBits=%s" % (expBits, maxBits))
72 self.expId = expId
73 self.expBits = expBits
74 self.maxBits = maxBits
76 @property
77 def unusedBits(self):
78 return self.maxBits - self.expBits