"""
Constants and utilities for handling HEP units.
"""
from pdg.errors import PdgApiError
HBAR_IN_GEV_S = 6.582E-25
UNIT_CONVERSION_FACTORS = {
'meV': (1E-3, 'eV'),
'eV': (1E0, 'eV'),
'keV': (1E3, 'eV'),
'MeV': (1E6, 'eV'),
'GeV': (1E9, 'eV'),
'TeV': (1E12, 'eV'),
'PeV': (1E15, 'eV'),
'u': (931.49410242E6, 'eV'),
's': (1E0, 's'),
'yr': (31536000, 's'),
'year': (31536000, 's'),
'years': (31536000, 's'),
}
[docs]def convert(value, old_units=None, new_units=None):
"""Utility to convert value to a different unit."""
if new_units is None:
return value
else:
try:
old_factor = UNIT_CONVERSION_FACTORS[old_units]
except KeyError:
raise PdgApiError('Cannot convert from %s' % old_units)
try:
new_factor = UNIT_CONVERSION_FACTORS[new_units]
except KeyError:
raise PdgApiError('Cannot convert to %s' % new_units)
if old_factor[1] != new_factor[1]:
raise PdgApiError('Illegal unit conversion from %s to %s', old_factor[1], new_factor[1])
return value * old_factor[0] / new_factor[0]