102 lines
3.4 KiB
Python
102 lines
3.4 KiB
Python
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#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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# Copyright 2014 California Institute of Technology. ALL RIGHTS RESERVED.
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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#
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# United States Government Sponsorship acknowledged. This software is subject to
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# U.S. export control laws and regulations and has been classified as 'EAR99 NLR'
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# (No [Export] License Required except when exporting to an embargoed country,
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# end user, or in support of a prohibited end use). By downloading this software,
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# the user agrees to comply with all applicable U.S. export laws and regulations.
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# The user has the responsibility to obtain export licenses, or other export
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# authority as may be required before exporting this software to any 'EAR99'
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# embargoed foreign country or citizen of those countries.
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#
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# Author: Eric Belz
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#~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
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"""The unit module.
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The rdf.data.entries.RDFField.__new__ only needs access to the
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SI function-- which identifies units and converts them to nominal
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inputs.
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See SI.__doc__ on how Units are used.
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"""
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## \namespace rdf.units RDF units as spec'd
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from iscesys.Parsers.rdf.units.physical_quantity import Unit
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from iscesys.Parsers.rdf.units import addendum
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from iscesys.Parsers.rdf.language import errors
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## The global unit glossary dictionary:[symbol]->converter function
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GLOSSARY = Unit.Glossary
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## Convert (value, units) to SI pair - this is the interface to RDField
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## Search various places for units...(TBD).
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## \param value A float in units
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## \param units a string describing the units
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## \retval (converter(value),converter.si_unit) The new value in the right units
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def SI(value, units):
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"""
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Using Units:
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Unit instance are instance of <str>-- hence you can compare them or use them
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as keys in a dictionary. Hence:
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>>>km = physical_quantity.Length('km', 1000)
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is a string == 'km', and it is a function that multiplies by 1000.
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Thus: SI just looks in a dictionary of UNITS, c.f:
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{km : km}['km']
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which returns km, such that:
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>>>print km(1)
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1000.
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Sweet.
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See physical_quanity on how to make your own units and how to put them in
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the GLOASSRY.
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"""
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try:
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converter = GLOSSARY[units]
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except KeyError:
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try:
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converter = runtime_units()[units]
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except KeyError:
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# raise errors.FatalUnitError to stop.
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raise errors.UnknownUnitWarning
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return converter(value), converter.si_unit
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## A function to read user defined units at runtime (after import-- otherwise
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## it's cyclic)-- format is provisional.
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def runtime_units(src='units.rdf'):
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"""read units from units.rdf:
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mym (m) {length} = 10000 ! A Myriameters is 10 K
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"""
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from iscesys.Parsers.rdf import RDF
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try:
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result = RDF.fromfile(src)
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except IOError:
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result = {}
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return result
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