def scale(base, kind, prefixes="", multiplier=1):
"""
Define a scale of similar quantities.
"""
base, abbrev = base.split('/')
res = []
for prefix in ['', *prefixes]:
q = Quantity(_names[prefix] + base, abbrev=abbrev)
q.set_dimension(kind[0])
q.set_scale_factor(multiplier * _factor[prefix] * kind[1])
res.append(q)
return res if prefixes else res[0]
def derive_unit(expr, name=None):
"""Derive SI-unit from an expression, omitting scale factors."""
from essm.variables import Variable
from essm.variables.utils import extract_variables
from sympy.physics.units import Dimension
from sympy.physics.units.dimensions import dimsys_SI
variables = extract_variables(expr)
for var1 in variables:
q1 = Quantity('q_' + str(var1))
q1.set_dimension(
Dimension(Quantity.get_dimensional_expr(var1.definition.unit)))
q1.set_scale_factor(var1.definition.unit)
expr = expr.xreplace({var1: q1})
dim = Dimension(Quantity.get_dimensional_expr(expr))
return functools.reduce(
operator.mul,
(SI_DIMENSIONS[d]**p
for d, p in dimsys_SI.get_dimensional_dependencies(dim).items()), 1)
def test_prefix_operations():
m = PREFIXES['m']
k = PREFIXES['k']
M = PREFIXES['M']
dodeca = Prefix('dodeca', 'dd', 1, base=12)
assert m * k == 1
assert k * k == M
assert 1 / m == k
assert k / m == M
assert dodeca * dodeca == 144
assert 1 / dodeca == S.One / 12
assert k / dodeca == S(1000) / 12
assert dodeca / dodeca == 1
m = Quantity("fake_meter")
m.set_dimension(S.One)
m.set_scale_factor(S.One)
assert dodeca * m == 12 * m
assert dodeca / m == 12 / m
expr1 = kilo * 3
assert isinstance(expr1, Mul)
assert (expr1).args == (3, kilo)
expr2 = kilo * x
assert isinstance(expr2, Mul)
assert (expr2).args == (x, kilo)
expr3 = kilo / 3
assert isinstance(expr3, Mul)
assert (expr3).args == (Rational(1, 3), kilo)
assert (expr3).args == (S.One / 3, kilo)
expr4 = kilo / x
assert isinstance(expr4, Mul)
assert (expr4).args == (1 / x, kilo)
def test_prefix_operations():
m = PREFIXES['m']
k = PREFIXES['k']
M = PREFIXES['M']
dodeca = Prefix('dodeca', 'dd', 1, base=12)
assert m * k == 1
assert k * k == M
assert 1 / m == k
assert k / m == M
assert dodeca * dodeca == 144
assert 1 / dodeca == S(1) / 12
assert k / dodeca == S(1000) / 12
assert dodeca / dodeca == 1
m = Quantity("fake_meter")
m.set_dimension(S.One)
m.set_scale_factor(S.One)
assert dodeca * m == 12 * m
assert dodeca / m == 12 / m
expr1 = kilo * 3
assert isinstance(expr1, Mul)
assert (expr1).args == (3, kilo)
expr2 = kilo * x
assert isinstance(expr2, Mul)
assert (expr2).args == (x, kilo)
expr3 = kilo / 3
assert isinstance(expr3, Mul)
assert (expr3).args == (S(1)/3, kilo)
expr4 = kilo / x
assert isinstance(expr4, Mul)
assert (expr4).args == (1/x, kilo)
def test_prefix_unit():
m = Quantity("fake_meter", abbrev="m")
m.set_dimension(length)
m.set_scale_factor(1)
pref = {"m": PREFIXES["m"], "c": PREFIXES["c"], "d": PREFIXES["d"]}
q1 = Quantity("millifake_meter", abbrev="mm")
q2 = Quantity("centifake_meter", abbrev="cm")
q3 = Quantity("decifake_meter", abbrev="dm")
q1.set_dimension(length)
q1.set_dimension(length)
q1.set_dimension(length)
q1.set_scale_factor(PREFIXES["m"])
q1.set_scale_factor(PREFIXES["c"])
q1.set_scale_factor(PREFIXES["d"])
res = [q1, q2, q3]
prefs = prefix_unit(m, pref)
assert set(prefs) == set(res)
assert set(map(lambda x: x.abbrev, prefs)) == set(symbols("mm,cm,dm"))
def test_prefix_unit():
m = Quantity("fake_meter", abbrev="m")
m.set_dimension(length)
m.set_scale_factor(1)
pref = {"m": PREFIXES["m"], "c": PREFIXES["c"], "d": PREFIXES["d"]}
q1 = Quantity("millifake_meter", abbrev="mm")
q2 = Quantity("centifake_meter", abbrev="cm")
q3 = Quantity("decifake_meter", abbrev="dm")
q1.set_dimension(length)
q1.set_dimension(length)
q1.set_dimension(length)
q1.set_scale_factor(PREFIXES["m"])
q1.set_scale_factor(PREFIXES["c"])
q1.set_scale_factor(PREFIXES["d"])
res = [q1, q2, q3]
prefs = prefix_unit(m, pref)
assert set(prefs) == set(res)
assert set(map(lambda x: x.abbrev, prefs)) == set(symbols("mm,cm,dm"))
import operator as op
from lark import Lark, InlineTransformer
from sympy import S
from sympy.physics import units
from sympy.physics.units import Quantity
from sympy.physics.units.dimensions import dimsys_SI
from sidekick import namespace
DIMENSIONLESS = Quantity("dimensionless")
DIMENSIONLESS.set_dimension(S.One)
DIMENSIONLESS.set_scale_factor(S.One)
SIMPY_UNITS = {k: v for k, v in vars(units).items() if not k.startswith('_')}
UNITS = namespace(**SIMPY_UNITS, )
grammar = Lark(r"""
?start : expr
| NUMBER -> dimensionless
?expr : expr "*" atom -> mul
| expr atom -> mul
| expr "/" atom -> div
| atom
?atom : name "^" number -> pow
| name number -> pow
| name
name : NAME
number : NUMBER