"""
Utilities for PDG API.
"""
from pdg.errors import PdgNoDataError, PdgAmbiguousValueError, PdgRoundingError
import math
[docs]
def pdg_round(value, error):
"""Return (value, error) as numbers rounded following PDG rounding rules."""
# FIXME: might switch to returning decimal.Decimal rather than floats
if error <= 0.:
raise PdgRoundingError('PDG rounding requires error larger than zero')
log = math.log10(abs(error))
if abs(error) < 1.0 and int(log) != log:
power = int(log)
else:
power = int(log) + 1
reduced_error = error * 10 ** (-power)
if reduced_error < 0.355:
n_digits = 2
elif reduced_error < 0.950:
n_digits = 1
else:
reduced_error = 0.1
power += 1
n_digits = 2
new_error = round(reduced_error, n_digits) * 10 ** power
new_value = round(value * 10 ** (-power), n_digits) * 10 ** power
return new_value, new_error
[docs]
def parse_id(pdgid):
"""Parse PDG Identifier and return (normalized base identifier, edition)."""
try:
baseid, edition = pdgid.split('/')
except ValueError:
baseid = pdgid
edition = None
return baseid.upper(), edition
[docs]
def base_id(pdgid):
"""Return normalized base part of PDG Identifier."""
return parse_id(pdgid)[0]
[docs]
def make_id(baseid, edition=None):
"""Return normalized full PDG Identifier, possibly including edition."""
if baseid is None:
return None
if edition is None:
return baseid.upper()
else:
return ('%s/%s' % (baseid, edition)).upper()
[docs]
def best(properties, pedantic=False, quantity=None):
"""Return the "best" property from an iterable of properties, or raise an exception.
best does (pedantic=False) or does not (pedantic=True) make assumptions about what the best property might
be in cases where the choice may be ambiguous. In the latter case, a PdgAmbiguous exception is raised while in the
former case the best property is determined based on data flags and position in the Summary Tables.
PdgNoDataError will be raised if there is no property that qualifies as best one.
quantity is an optional string that in case of an exception will describe the property being sought.
"""
for_what = ' for %s' % quantity if quantity else ''
props_without_alternates = [p for p in properties if 'A' not in p.data_flags]
# in non-pedantic mode, filter out "special" values
if not pedantic:
props_without_alternates = [p for p in props_without_alternates
if 's' not in p.data_flags]
if len(props_without_alternates) == 0:
raise PdgNoDataError('No best property found%s' % for_what)
elif len(props_without_alternates) == 1:
return props_without_alternates[0]
else:
if pedantic:
err = 'Ambiguous best property%s' % for_what
raise PdgAmbiguousValueError(err)
else:
props_best = [p for p in props_without_alternates if 'D' in p.data_flags]
if len(props_best) >= 1:
return props_best[0]
else:
return props_without_alternates[0]