Source code for astropy.units.format.cds

# 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 re

from astropy.units.utils import is_effectively_unity
from astropy.utils import classproperty, parsing
from astropy.utils.misc import did_you_mean

from . import core, utils
from .base import Base


[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 <https://vizier.u-strasbg.fr/viz-bin/Unit>`_. This format is used by VOTable up to version 1.2. """ _tokens = ( "PRODUCT", "DIVISION", "OPEN_PAREN", "CLOSE_PAREN", "OPEN_BRACKET", "CLOSE_BRACKET", "X", "SIGN", "UINT", "UFLOAT", "UNIT", "DIMENSIONLESS", ) @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 import units as u from astropy.units import cds names = {} for key, val in cds.__dict__.items(): if isinstance(val, u.UnitBase): names[key] = val return names @classmethod def _make_lexer(cls): tokens = cls._tokens t_PRODUCT = r"\." t_DIVISION = r"/" t_OPEN_PAREN = r"\(" t_CLOSE_PAREN = r"\)" t_OPEN_BRACKET = r"\[" t_CLOSE_BRACKET = r"\]" # 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 def t_DIMENSIONLESS(t): r"---|-" # These are separate from t_UNIT since they cannot have a prefactor. 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}") return parsing.lex( lextab="cds_lextab", package="astropy/units", reflags=int(re.UNICODE) ) @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/>`_. """ tokens = cls._tokens def p_main(p): """ main : factor combined_units | combined_units | DIMENSIONLESS | OPEN_BRACKET combined_units CLOSE_BRACKET | OPEN_BRACKET DIMENSIONLESS CLOSE_BRACKET | factor """ from astropy.units import dex from astropy.units.core import Unit if len(p) == 3: p[0] = Unit(p[1] * p[2]) elif len(p) == 4: p[0] = dex(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() return parsing.yacc(tabmodule="cds_parsetab", package="astropy/units") @classmethod def _get_unit(cls, t): try: return cls._parse_unit(t.value) except ValueError as e: registry = core.get_current_unit_registry() if t.value in registry.aliases: return registry.aliases[t.value] raise ValueError(f"At col {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(f"{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 == core.dimensionless_unscaled: return "---" elif is_effectively_unity(unit.scale * 100.0): 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