import collections
import math
import numpy as np
from ..core.errors import UnitsError
__all__ = ['Units']
[docs]class Units:
"""A singleton class for unit converter.
All values are based on `2014 CODATA recommended values <http://physics.nist.gov/cuu/Constants>`_.
The following constants and units are supported:
* constants:
- ``speed_of_light`` (also ``c``)
- ``electron_charge`` (also ``e``)
- ``Avogadro_constant`` (also ``NA``)
- ``Bohr_radius``
* distance:
- ``Angstrom``, ``A``
- ``Bohr``, ``au``, ``a.u.``
- ``nm``
- ``pm``
* reciprocal distance:
- ``1/Angstrom``, ``1/A``, ``Angstrom^-1``, ``A^-1``,
- ``1/Bohr``, ``Bohr^-1``
* angle:
- ``degree``, ``deg``,
- ``radian``, ``rad``,
- ``grad``
- ``circle``
* energy:
- ``au``, ``a.u.``, ``Hartree``
- ``eV``
- ``kcal/mol``
- ``kJ/mol``
- ``cm^-1``, ``cm-1``
- ``K``, ``Kelvin``
* dipole moment:
- ``au``, ``a.u.``
- ``Cm``
- ``Debye``, ``D``
* forces:
- All energy units divided by angstrom or bohr, for example
- ``eV/angstrom``
- ``hartree/bohr``
* hessian:
- All energy units divided by angstrom^2 or bohr^2, for example
- ``eV/angstrom^2``
- ``hartree/bohr^2``
* pressure:
- All energy units divided by angstrom^3 or bohr^3, for example
- ``eV/angstrom^3``
- ``hartree/bohr^3``
- And some more:
- ``Pa``
- ``GPa``
- ``bar``
- ``atm``
Example::
>>> print(Units.constants['speed_of_light'])
299792458
>>> print(Units.constants['e'])
1.6021766208e-19
>>> print(Units.convert(123, 'angstrom', 'bohr'))
232.436313431
>>> print(Units.convert([23.32, 145.0, -34.7], 'kJ/mol', 'kcal/mol'))
[5.573613766730401, 34.655831739961755, -8.293499043977056]
>>> print(Units.conversion_ratio('kcal/mol', 'kJ/mol'))
4.184
"""
constants = {}
constants['Bohr_radius'] = 0.529177210903 #http://physics.nist.gov/cgi-bin/cuu/Value?bohrrada0
constants['Avogadro_constant'] = constants['NA'] = 6.022140857e23 #http://physics.nist.gov/cgi-bin/cuu/Value?na
constants['speed_of_light'] = constants['c'] = 299792458 #http://physics.nist.gov/cgi-bin/cuu/Value?c
constants['electron_charge'] = constants['e'] = 1.6021766208e-19 #http://physics.nist.gov/cgi-bin/cuu/Value?e
constants['Boltzmann'] = constants['k_B'] = 1.380649e-23 #J/K
distance = {}
distance['A'] = distance['Angstrom'] = 1.0
distance['Bohr'] = distance['a.u.'] = distance['au'] = 1.0 / constants['Bohr_radius']
distance['nm'] = distance['A'] / 10.0
distance['pm'] = distance['A'] * 100.0
distance['m'] = distance['A'] * 1e-10
rec_distance = {}
rec_distance['1/A'] = rec_distance['1/Ang'] = rec_distance['1/Angstrom'] = rec_distance['A^-1'] = rec_distance['Ang^-1'] = rec_distance['Angstrom^-1'] = 1.0
rec_distance['1/m'] = rec_distance['m^-1'] = 1e10
rec_distance['1/Bohr'] = rec_distance['Bohr^-1'] = constants['Bohr_radius']
energy = {}
energy['au'] = energy['a.u.'] = energy['Hartree'] = energy['Ha'] = 1.0
energy['eV'] = 27.211386245988 #http://physics.nist.gov/cgi-bin/cuu/Value?hrev
energy['kJ/mol'] = 4.359744650e-21 * constants['NA'] #http://physics.nist.gov/cgi-bin/cuu/Value?hrj
energy['J'] = 4.359744650e-18
energy['kcal/mol'] = energy['kJ/mol'] / 4.184
energy['cm^-1'] = energy['cm-1'] = 219474.6313702 #http://physics.nist.gov/cgi-bin/cuu/Value?hrminv
energy['K'] = energy['J'] / constants['k_B']
mass = {}
mass['au'] = mass['a.u.'] = mass['amu'] = 1.0
mass['kg'] = 1.66053906660e-27
mass['g'] = mass['kg'] * 1e3
time = {}
time['s'] = 1.0
time['ms'] = time['s'] * 1e3
time['us'] = time['s'] * 1e6
time['ns'] = time['s'] * 1e9
time['ps'] = time['s'] * 1e12
time['fs'] = time['s'] * 1e15
time['au'] = time['a.u.'] = time['s'] / 2.4188843265857e-17 #https://physics.nist.gov/cgi-bin/cuu/Value?aut
angle = {}
angle['degree'] = angle['deg'] = 1.0
angle['radian'] = angle['rad'] = math.pi / 180.0
angle['grad'] = 100.0 / 90.0
angle['circle'] = 1.0 / 360.0
dipole = {}
dipole['au'] = dipole['a.u.'] = 1.0
dipole['Cm'] = constants['e'] * constants['Bohr_radius'] * 1e-10
dipole['Debye'] = dipole['D'] = dipole['Cm'] * constants['c']* 1e21
forces = {}
hessian = {}
stress = {}
for k,v in energy.items():
forces[k+'/Angstrom'] = forces[k+'/Ang'] = forces[k+'/A'] = v * rec_distance['1/Angstrom']
hessian[k+'/Angstrom^2'] = hessian[k+'/Ang^2'] = hessian[k+'/A^2'] = v * rec_distance['1/Angstrom']**2
stress[k+'/Angstrom^3'] = stress[k+'/Ang^3'] = stress[k+'/A^3'] = v * rec_distance['1/Angstrom']**3
forces[k+'/bohr'] = forces[k+'/au'] = forces[k+'/a.u.'] = v * rec_distance['1/Bohr']
hessian[k+'/bohr^2'] = hessian[k+'/au^2'] = hessian[k+'/a.u.^2'] = v * rec_distance['1/Bohr']**2
stress[k+'/bohr^3'] = stress[k+'/au^3'] = stress[k+'/a.u.^3'] = v * rec_distance['1/Bohr']**3
forces[k+'/m'] = v * rec_distance['1/m']
hessian[k+'/m^2'] = v * rec_distance['1/m']**2
stress[k+'/m^3'] = v * rec_distance['1/m']**3
forces['au'] = forces['a.u.'] = forces['Ha/bohr']
hessian['au'] = hessian['a.u.'] = hessian['Ha/bohr^2']
stress['au'] = stress['a.u.'] = stress['Ha/bohr^3']
stress['Pa'] = stress['J/m^3']
stress['GPa'] = stress['Pa'] * 1e-9
stress['bar'] = stress['Pa'] * 1e-5
stress['atm'] = stress['bar'] / 1.01325
dicts = {}
dicts['distance'] = distance
dicts['energy'] = energy
dicts['mass'] = mass
dicts['time'] = time
dicts['angle'] = angle
dicts['dipole'] = dipole
dicts['reciprocal distance'] = rec_distance
dicts['forces'] = forces
dicts['hessian'] = hessian
dicts['stress'] = stress
# Precompute a dict mapping lowercased unit names to quantityName:conversionFactor pairs
quantities_for_unit = {}
for quantity in dicts:
for unit, factor in dicts[quantity].items():
unit = unit.lower()
if unit not in quantities_for_unit:
quantities_for_unit[unit] = {}
quantities_for_unit[unit][quantity] = factor
[docs] def __init__(self):
raise UnitsError('Instances of Units cannot be created')
@classmethod
def find_unit(cls, unit):
ret = {}
u = unit.lower()
quantities = cls.quantities_for_unit.get(u, {})
for quantity in quantities:
for k in cls.dicts[quantity]:
if k.lower() == u:
ret[quantity] = k
break
return ret
[docs] @classmethod
def conversion_ratio(cls, inp, out):
"""Return conversion ratio from unit *inp* to *out*."""
if inp == out: return 1.0
inps = cls.quantities_for_unit.get(inp.lower(), {})
outs = cls.quantities_for_unit.get(out.lower(), {})
common = set(inps.keys()) & set(outs.keys())
if len(common) > 0:
quantity = common.pop()
return outs[quantity]/inps[quantity]
else:
if len(inps) == 0 and len(outs) == 0:
raise UnitsError("Unsupported units: '{}' and '{}'".format(inp, out))
if len(inps) > 0 and len(outs) > 0:
raise UnitsError("Invalid unit conversion: '{}' is a unit of {} and '{}' is a unit of {}".format(inp, ', '.join(list(inps.keys())), out, ', '.join(list(outs.keys()))))
else: #exactly one of (inps,outs) empty
invalid, nonempty = (out,inps) if len(inps) else (inp,outs)
if len(nonempty) == 1:
quantity = list(nonempty.keys())[0]
raise UnitsError("Invalid unit conversion: {} is not supported. Supported units for {}: {}".format(invalid, quantity, ', '.join(list(cls.dicts[quantity].keys()))))
else:
raise UnitsError("Invalid unit conversion: {} is not a supported unit for {}".format(invalid, ', '.join(list(nonempty.keys()))))
[docs] @classmethod
def convert(cls, value, inp, out):
"""Convert *value* from unit *inp* to *out*.
*value* can be a single number or a container (list, tuple, numpy.array etc.). In the latter case a container of the same type and length is returned. Conversion happens recursively, so this method can be used to convert, for example, a list of lists of numbers, or any other hierarchical container structure. Conversion is applied on all levels, to all values that are numbers (also numpy number types). All other values (strings, bools etc.) remain unchanged.
"""
if value is None or isinstance(value, (bool, str)) or inp == out:
return value
if isinstance(value, collections.abc.Iterable):
t = type(value)
if t == np.ndarray:
t = np.array
v = [cls.convert(i, inp, out) for i in value]
return t(v)
if isinstance(value, (int, float, np.generic)):
return value * cls.conversion_ratio(inp,out)
return value
[docs] @classmethod
def ascii2unicode(cls, string):
"""
Converts '^2' to '²' etc., for prettier printing of units.
"""
if string is None:
return ''
ret = string.replace('^-1', '⁻¹').replace('angstrom', 'Å').replace('^2','²').replace('^3','³').replace('degree', '°').replace('deg.', '°')
return ret