def set_quantity(quantity, dimension, scale_factor):
"""
Set value and unit to physical quantity.
Example:
>>> import sympy.physics.units as un
>>> from sympy.functions import *
>>> from sympy.physics.units import Quantity
>>> from utils import *
>>> from sympy.physics.units import convert_to
>>>
>>> E = Quantity("E")
>>> c = Quantity("c")
>>> set_quantity(E, un.energy, 2.15e12 * un.kilo * un.watts * un.hour)
>>> set_quantity(c, un.speed, 3.00e8 * un.m / un.s)
>>> E = convert_to(E, un.joule).n()
>>> m = E/c**2
7.74e+18*joule/c**2
convert_to(m, un.kg).n()
86.0*kilogram
:param quantity: physical quantity, for example length, mass or energy
:param dimension: time, length, mass ... based on sympy.physics.units
:param scale_factor: value to be set to `quantity` parameter
"""
SI.set_quantity_dimension(quantity, dimension)
SI.set_quantity_scale_factor(quantity, scale_factor)
def test_dimensions_of_expressions(self):
a = Quantity("a")
SI.set_quantity_dimension(a, length)
t = Quantity("t")
SI.set_quantity_dimension(t, time)
res = a**2 / t
# we can now determine the physical dimension of res
res_dim = SI.get_dimensional_expr(res)
self.assertTrue(dimsys_SI.equivalent_dims(res_dim, length**2 / time))
# In parameter dicts we can describe values along with units
a_val = Quantity("a_val")
SI.set_quantity_dimension(a_val, length)
SI.set_quantity_scale_factor(a_val, 5 * meter)
parameter_dict = {a: 5 * meter, t: 4 * second}
res_val = res.subs(parameter_dict)
# we can now determine the physical dimension of res_val
# and check it against the expected
print(SI.get_dimensional_expr(res_val))
self.assertTrue(
dimsys_SI.equivalent_dims(SI.get_dimensional_expr(res),
SI.get_dimensional_expr(res_val)))
def test_issue_22164():
warnings.simplefilter("error")
dm = Quantity("dm")
SI.set_quantity_dimension(dm, length)
SI.set_quantity_scale_factor(dm, 1)
bad_exp = Quantity("bad_exp")
SI.set_quantity_dimension(bad_exp, length)
SI.set_quantity_scale_factor(bad_exp, 1)
expr = dm**bad_exp
# deprecation warning is not expected here
SI._collect_factor_and_dimension(expr)
from sympy import symbols, solve, Eq, pretty_print
from sympy.physics.units import Quantity, mass, acceleration, power, velocity
from sympy.physics.units import convert_to
from sympy.physics.units import kilo
from sympy.physics.units import km, hour, m, s, kg, W
from sympy.physics.units.systems import SI
a = symbols("a")
m_ = Quantity("m")
v = Quantity("v")
W_ = Quantity("W")
SI.set_quantity_dimension(a, acceleration)
SI.set_quantity_dimension(m_, mass)
SI.set_quantity_scale_factor(m_, 1000*kg)
SI.set_quantity_dimension(v, velocity)
SI.set_quantity_scale_factor(v, 60*km/hour)
SI.set_quantity_dimension(W_, power)
SI.set_quantity_scale_factor(W_, 120*kilo*W)
eq = Eq(W_, m_*a*v)
result = solve(eq, a)[0]
pretty_print(result)
pretty_print(convert_to(result, m / s ** 2).n())
init_printing()
Wo = symbols("Wo")
v = symbols("v")
rho = Quantity("rho")
s = Quantity("s")
g = Quantity("g")
h1 = Quantity("h1")
h2 = Quantity("h2")
etha = Quantity("etha")
theta = Quantity("theta")
SI.set_quantity_dimension(rho, mass / length**3)
SI.set_quantity_scale_factor(rho, 1.0 * un.grams / un.cm**3)
SI.set_quantity_dimension(s, length**2)
SI.set_quantity_scale_factor(s, 35.0 * un.cm**2)
SI.set_quantity_dimension(h1, length)
SI.set_quantity_scale_factor(h1, 2.4 * un.meters)
SI.set_quantity_dimension(h2, length)
SI.set_quantity_scale_factor(h2, 4.8 * un.meters)
SI.set_quantity_dimension(g, acceleration)
SI.set_quantity_scale_factor(g, 9.81 * un.m / un.s**2)
SI.set_quantity_dimension(etha, One)
SI.set_quantity_scale_factor(etha, 0.6)