Source code for astropy.units.format.cds

# -*- coding: utf-8 -*-
# Licensed under a 3-clause BSD style license - see LICNSE.rst

# This module includes files automatically generated from ply (these end in
# _lextab.py and _parsetab.py). To generate these files, remove them from this
# folder, then build astropy and run the tests in-place:
#
#   python setup.py build_ext --inplace
#   pytest astropy/units
#
# You can then commit the changes to the re-generated _lextab.py and
# _parsetab.py files.

"""
Handles the CDS string format for units
"""


import operator
import os
import re


from .base import Base
from . import core, utils
from astropy.units.utils import is_effectively_unity
from astropy.utils import classproperty
from astropy.utils.misc import did_you_mean


# TODO: Support logarithmic units using bracketed syntax

[docs]class CDS(Base): """ Support the `Centre de Données astronomiques de Strasbourg <http://cds.u-strasbg.fr/>`_ `Standards for Astronomical Catalogues 2.0 <http://vizier.u-strasbg.fr/vizier/doc/catstd-3.2.htx>`_ format, and the `complete set of supported units <http://vizier.u-strasbg.fr/cgi-bin/Unit>`_. This format is used by VOTable up to version 1.2. """ _tokens = ( 'PRODUCT', 'DIVISION', 'OPEN_PAREN', 'CLOSE_PAREN', 'X', 'SIGN', 'UINT', 'UFLOAT', 'UNIT' ) @classproperty(lazy=True) def _units(cls): return cls._generate_unit_names() @classproperty(lazy=True) def _parser(cls): return cls._make_parser() @classproperty(lazy=True) def _lexer(cls): return cls._make_lexer() @staticmethod def _generate_unit_names(): from astropy.units import cds from astropy import units as u names = {} for key, val in cds.__dict__.items(): if isinstance(val, u.UnitBase): names[key] = val return names @classmethod def _make_lexer(cls): from astropy.extern.ply import lex tokens = cls._tokens t_PRODUCT = r'\.' t_DIVISION = r'/' t_OPEN_PAREN = r'\(' t_CLOSE_PAREN = r'\)' # NOTE THE ORDERING OF THESE RULES IS IMPORTANT!! # Regular expression rules for simple tokens def t_UFLOAT(t): r'((\d+\.?\d+)|(\.\d+))([eE][+-]?\d+)?' if not re.search(r'[eE\.]', t.value): t.type = 'UINT' t.value = int(t.value) else: t.value = float(t.value) return t def t_UINT(t): r'\d+' t.value = int(t.value) return t def t_SIGN(t): r'[+-](?=\d)' t.value = float(t.value + '1') return t def t_X(t): # multiplication for factor in front of unit r'[x×]' return t def t_UNIT(t): r'\%|°|\\h|((?!\d)\w)+' t.value = cls._get_unit(t) return t t_ignore = '' # Error handling rule def t_error(t): raise ValueError( f"Invalid character at col {t.lexpos}") lexer_exists = os.path.exists(os.path.join(os.path.dirname(__file__), 'cds_lextab.py')) lexer = lex.lex(optimize=True, lextab='cds_lextab', outputdir=os.path.dirname(__file__), reflags=int(re.UNICODE)) if not lexer_exists: cls._add_tab_header('cds_lextab') return lexer @classmethod def _make_parser(cls): """ The grammar here is based on the description in the `Standards for Astronomical Catalogues 2.0 <http://vizier.u-strasbg.fr/vizier/doc/catstd-3.2.htx>`_, which is not terribly precise. The exact grammar is here is based on the YACC grammar in the `unity library <https://bitbucket.org/nxg/unity/>`_. """ from astropy.extern.ply import yacc tokens = cls._tokens def p_main(p): ''' main : factor combined_units | combined_units | factor ''' from astropy.units.core import Unit if len(p) == 3: p[0] = Unit(p[1] * p[2]) else: p[0] = Unit(p[1]) def p_combined_units(p): ''' combined_units : product_of_units | division_of_units ''' p[0] = p[1] def p_product_of_units(p): ''' product_of_units : unit_expression PRODUCT combined_units | unit_expression ''' if len(p) == 4: p[0] = p[1] * p[3] else: p[0] = p[1] def p_division_of_units(p): ''' division_of_units : DIVISION unit_expression | unit_expression DIVISION combined_units ''' if len(p) == 3: p[0] = p[2] ** -1 else: p[0] = p[1] / p[3] def p_unit_expression(p): ''' unit_expression : unit_with_power | OPEN_PAREN combined_units CLOSE_PAREN ''' if len(p) == 2: p[0] = p[1] else: p[0] = p[2] def p_factor(p): ''' factor : signed_float X UINT signed_int | UINT X UINT signed_int | UINT signed_int | UINT | signed_float ''' if len(p) == 5: if p[3] != 10: raise ValueError( "Only base ten exponents are allowed in CDS") p[0] = p[1] * 10.0 ** p[4] elif len(p) == 3: if p[1] != 10: raise ValueError( "Only base ten exponents are allowed in CDS") p[0] = 10.0 ** p[2] elif len(p) == 2: p[0] = p[1] def p_unit_with_power(p): ''' unit_with_power : UNIT numeric_power | UNIT ''' if len(p) == 2: p[0] = p[1] else: p[0] = p[1] ** p[2] def p_numeric_power(p): ''' numeric_power : sign UINT ''' p[0] = p[1] * p[2] def p_sign(p): ''' sign : SIGN | ''' if len(p) == 2: p[0] = p[1] else: p[0] = 1.0 def p_signed_int(p): ''' signed_int : SIGN UINT ''' p[0] = p[1] * p[2] def p_signed_float(p): ''' signed_float : sign UINT | sign UFLOAT ''' p[0] = p[1] * p[2] def p_error(p): raise ValueError() parser_exists = os.path.exists(os.path.join(os.path.dirname(__file__), 'cds_parsetab.py')) parser = yacc.yacc(debug=False, tabmodule='cds_parsetab', outputdir=os.path.dirname(__file__), write_tables=True) if not parser_exists: cls._add_tab_header('cds_parsetab') return parser @classmethod def _get_unit(cls, t): try: return cls._parse_unit(t.value) except ValueError as e: raise ValueError( "At col {}, {}".format( t.lexpos, str(e))) @classmethod def _parse_unit(cls, unit, detailed_exception=True): if unit not in cls._units: if detailed_exception: raise ValueError( "Unit '{}' not supported by the CDS SAC " "standard. {}".format( unit, did_you_mean( unit, cls._units))) else: raise ValueError() return cls._units[unit]
[docs] @classmethod def parse(cls, s, debug=False): if ' ' in s: raise ValueError('CDS unit must not contain whitespace') if not isinstance(s, str): s = s.decode('ascii') # This is a short circuit for the case where the string # is just a single unit name try: return cls._parse_unit(s, detailed_exception=False) except ValueError: try: return cls._parser.parse(s, lexer=cls._lexer, debug=debug) except ValueError as e: if str(e): raise ValueError(str(e)) else: raise ValueError("Syntax error")
@staticmethod def _get_unit_name(unit): return unit.get_format_name('cds') @classmethod def _format_unit_list(cls, units): out = [] for base, power in units: if power == 1: out.append(cls._get_unit_name(base)) else: out.append('{}{}'.format( cls._get_unit_name(base), int(power))) return '.'.join(out)
[docs] @classmethod def to_string(cls, unit): # Remove units that aren't known to the format unit = utils.decompose_to_known_units(unit, cls._get_unit_name) if isinstance(unit, core.CompositeUnit): if(unit.physical_type == 'dimensionless' and is_effectively_unity(unit.scale*100.)): return '%' if unit.scale == 1: s = '' else: m, e = utils.split_mantissa_exponent(unit.scale) parts = [] if m not in ('', '1'): parts.append(m) if e: if not e.startswith('-'): e = "+" + e parts.append(f'10{e}') s = 'x'.join(parts) pairs = list(zip(unit.bases, unit.powers)) if len(pairs) > 0: pairs.sort(key=operator.itemgetter(1), reverse=True) s += cls._format_unit_list(pairs) elif isinstance(unit, core.NamedUnit): s = cls._get_unit_name(unit) return s