Source code for astropy.units.format.generic

# Licensed under a 3-clause BSD style license - see LICENSE.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 a "generic" string format for units
"""

import os
import re
import warnings

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


def _to_string(cls, unit):
    if isinstance(unit, core.CompositeUnit):
        parts = []

        if cls._show_scale and unit.scale != 1:
            parts.append('{0:g}'.format(unit.scale))

        if len(unit.bases):
            positives, negatives = utils.get_grouped_by_powers(
                unit.bases, unit.powers)
            if len(positives):
                parts.append(cls._format_unit_list(positives))
            elif len(parts) == 0:
                parts.append('1')

            if len(negatives):
                parts.append('/')
                unit_list = cls._format_unit_list(negatives)
                if len(negatives) == 1:
                    parts.append('{0}'.format(unit_list))
                else:
                    parts.append('({0})'.format(unit_list))

        return ' '.join(parts)
    elif isinstance(unit, core.NamedUnit):
        return cls._get_unit_name(unit)


[docs]class Generic(Base): """ A "generic" format. The syntax of the format is based directly on the FITS standard, but instead of only supporting the units that FITS knows about, it supports any unit available in the `astropy.units` namespace. """ _show_scale = True _tokens = ( 'DOUBLE_STAR', 'STAR', 'PERIOD', 'SOLIDUS', 'CARET', 'OPEN_PAREN', 'CLOSE_PAREN', 'FUNCNAME', 'UNIT', 'SIGN', 'UINT', 'UFLOAT' ) @classproperty(lazy=True) def _all_units(cls): return cls._generate_unit_names() @classproperty(lazy=True) def _units(cls): return cls._all_units[0] @classproperty(lazy=True) def _deprecated_units(cls): return cls._all_units[1] @classproperty(lazy=True) def _functions(cls): return cls._all_units[2] @classproperty(lazy=True) def _parser(cls): return cls._make_parser() @classproperty(lazy=True) def _lexer(cls): return cls._make_lexer() @classmethod def _make_lexer(cls): from astropy.extern.ply import lex tokens = cls._tokens t_STAR = r'\*' t_PERIOD = r'\.' t_SOLIDUS = r'/' t_DOUBLE_STAR = r'\*\*' t_CARET = 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) elif t.value.endswith('.'): t.type = 'UINT' t.value = int(t.value[:-1]) 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 # This needs to be a function so we can force it to happen # before t_UNIT def t_FUNCNAME(t): r'((sqrt)|(ln)|(exp)|(log)|(mag)|(dB)|(dex))(?=\ *\()' return t def t_UNIT(t): r"%|([YZEPTGMkhdcmunpfazy]?'((?!\d)\w)+')|((?!\d)\w)+" t.value = cls._get_unit(t) return t t_ignore = ' ' # Error handling rule def t_error(t): raise ValueError( "Invalid character at col {0}".format(t.lexpos)) lexer_exists = os.path.exists(os.path.join(os.path.dirname(__file__), 'generic_lextab.py')) lexer = lex.lex(optimize=True, lextab='generic_lextab', outputdir=os.path.dirname(__file__), reflags=int(re.UNICODE)) if not lexer_exists: cls._add_tab_header('generic_lextab') return lexer @classmethod def _make_parser(cls): """ The grammar here is based on the description in the `FITS standard <http://fits.gsfc.nasa.gov/standard30/fits_standard30aa.pdf>`_, Section 4.3, 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/>`_. This same grammar is used by the `"fits"` and `"vounit"` formats, the only difference being the set of available unit strings. """ from astropy.extern.ply import yacc tokens = cls._tokens def p_main(p): ''' main : product_of_units | factor product_of_units | factor product product_of_units | division_product_of_units | factor division_product_of_units | factor product division_product_of_units | inverse_unit | factor inverse_unit | factor product inverse_unit | factor ''' from astropy.units.core import Unit if len(p) == 2: p[0] = Unit(p[1]) elif len(p) == 3: p[0] = Unit(p[1] * p[2]) elif len(p) == 4: p[0] = Unit(p[1] * p[3]) def p_division_product_of_units(p): ''' division_product_of_units : division_product_of_units division product_of_units | product_of_units ''' from astropy.units.core import Unit if len(p) == 4: p[0] = Unit(p[1] / p[3]) else: p[0] = p[1] def p_inverse_unit(p): ''' inverse_unit : division unit_expression ''' p[0] = p[2] ** -1 def p_factor(p): ''' factor : factor_fits | factor_float | factor_int ''' p[0] = p[1] def p_factor_float(p): ''' factor_float : signed_float | signed_float UINT signed_int | signed_float UINT power numeric_power ''' if cls.name == 'fits': raise ValueError("Numeric factor not supported by FITS") if len(p) == 4: p[0] = p[1] * p[2] ** float(p[3]) elif len(p) == 5: p[0] = p[1] * p[2] ** float(p[4]) elif len(p) == 2: p[0] = p[1] def p_factor_int(p): ''' factor_int : UINT | UINT signed_int | UINT power numeric_power | UINT UINT signed_int | UINT UINT power numeric_power ''' if cls.name == 'fits': raise ValueError("Numeric factor not supported by FITS") if len(p) == 2: p[0] = p[1] elif len(p) == 3: p[0] = p[1] ** float(p[2]) elif len(p) == 4: if isinstance(p[2], int): p[0] = p[1] * p[2] ** float(p[3]) else: p[0] = p[1] ** float(p[3]) elif len(p) == 5: p[0] = p[1] * p[2] ** p[4] def p_factor_fits(p): ''' factor_fits : UINT power OPEN_PAREN signed_int CLOSE_PAREN | UINT power OPEN_PAREN UINT CLOSE_PAREN | UINT power signed_int | UINT power UINT | UINT SIGN UINT | UINT OPEN_PAREN signed_int CLOSE_PAREN ''' if p[1] != 10: if cls.name == 'fits': raise ValueError("Base must be 10") else: return if len(p) == 4: if p[2] in ('**', '^'): p[0] = 10 ** p[3] else: p[0] = 10 ** (p[2] * p[3]) elif len(p) == 5: p[0] = 10 ** p[3] elif len(p) == 6: p[0] = 10 ** p[4] def p_product_of_units(p): ''' product_of_units : unit_expression product product_of_units | unit_expression product_of_units | unit_expression ''' if len(p) == 2: p[0] = p[1] elif len(p) == 3: p[0] = p[1] * p[2] else: p[0] = p[1] * p[3] def p_unit_expression(p): ''' unit_expression : function | unit_with_power | OPEN_PAREN product_of_units CLOSE_PAREN ''' if len(p) == 2: p[0] = p[1] else: p[0] = p[2] def p_unit_with_power(p): ''' unit_with_power : UNIT power numeric_power | UNIT numeric_power | UNIT ''' if len(p) == 2: p[0] = p[1] elif len(p) == 3: p[0] = p[1] ** p[2] else: p[0] = p[1] ** p[3] def p_numeric_power(p): ''' numeric_power : sign UINT | OPEN_PAREN paren_expr CLOSE_PAREN ''' if len(p) == 3: p[0] = p[1] * p[2] elif len(p) == 4: p[0] = p[2] def p_paren_expr(p): ''' paren_expr : sign UINT | signed_float | frac ''' if len(p) == 3: p[0] = p[1] * p[2] else: p[0] = p[1] def p_frac(p): ''' frac : sign UINT division sign UINT ''' p[0] = (p[1] * p[2]) / (p[4] * p[5]) def p_sign(p): ''' sign : SIGN | ''' if len(p) == 2: p[0] = p[1] else: p[0] = 1.0 def p_product(p): ''' product : STAR | PERIOD ''' pass def p_division(p): ''' division : SOLIDUS ''' pass def p_power(p): ''' power : DOUBLE_STAR | CARET ''' p[0] = p[1] 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_function_name(p): ''' function_name : FUNCNAME ''' p[0] = p[1] def p_function(p): ''' function : function_name OPEN_PAREN main CLOSE_PAREN ''' if p[1] == 'sqrt': p[0] = p[3] ** 0.5 return elif p[1] in ('mag', 'dB', 'dex'): function_unit = cls._parse_unit(p[1]) # In Generic, this is callable, but that does not have to # be the case in subclasses (e.g., in VOUnit it is not). if callable(function_unit): p[0] = function_unit(p[3]) return raise ValueError("'{0}' is not a recognized function".format(p[1])) def p_error(p): raise ValueError() parser_exists = os.path.exists(os.path.join(os.path.dirname(__file__), 'generic_parsetab.py')) parser = yacc.yacc(debug=False, tabmodule='generic_parsetab', outputdir=os.path.dirname(__file__)) if not parser_exists: cls._add_tab_header('generic_parsetab') return parser @classmethod def _get_unit(cls, t): try: return cls._parse_unit(t.value) except ValueError as e: raise ValueError( "At col {0}, {1}".format( t.lexpos, str(e))) @classmethod def _parse_unit(cls, s, detailed_exception=True): registry = core.get_current_unit_registry().registry if s == '%': return registry['percent'] elif s in registry: return registry[s] if detailed_exception: raise ValueError( '{0} is not a valid unit. {1}'.format( s, did_you_mean(s, registry))) else: raise ValueError()
[docs] @classmethod def parse(cls, s, debug=False): if not isinstance(s, str): s = s.decode('ascii') result = cls._do_parse(s, debug=debug) if s.count('/') > 1: warnings.warn( "'{0}' contains multiple slashes, which is " "discouraged by the FITS standard".format(s), core.UnitsWarning) return result
@classmethod def _do_parse(cls, s, debug=False): try: # This is a short circuit for the case where the string # is just a single unit name return cls._parse_unit(s, detailed_exception=False) except ValueError as e: try: return cls._parser.parse(s, lexer=cls._lexer, debug=debug) except ValueError as e: if str(e): raise else: raise ValueError( "Syntax error parsing unit '{0}'".format(s)) @classmethod def _get_unit_name(cls, unit): return unit.get_format_name('generic') @classmethod def _format_unit_list(cls, units): out = [] units.sort(key=lambda x: cls._get_unit_name(x[0]).lower()) for base, power in units: if power == 1: out.append(cls._get_unit_name(base)) else: power = utils.format_power(power) if '/' in power: out.append('{0}({1})'.format( cls._get_unit_name(base), power)) else: out.append('{0}{1}'.format( cls._get_unit_name(base), power)) return ' '.join(out)
[docs] @classmethod def to_string(cls, unit): return _to_string(cls, unit)
[docs]class Unscaled(Generic): """ A format that doesn't display the scale part of the unit, other than that, it is identical to the `Generic` format. This is used in some error messages where the scale is irrelevant. """ _show_scale = False