def test_multiplication():
"""
Multiply two units.
"""
msun_mks = mass_sun_kg
pc_mks = m_per_pc
# Create symbols
msun_sym = Symbol("Msun", positive=True)
pc_sym = Symbol("pc", positive=True)
s_sym = Symbol("s", positive=True)
# Create units
u1 = Unit("Msun")
u2 = Unit("pc")
# Mul operation
u3 = u1 * u2
assert u3.expr == msun_sym * pc_sym
assert_allclose_units(u3.base_value, msun_mks * pc_mks, 1e-12)
assert u3.dimensions == mass * length
# Pow and Mul operations
u4 = Unit("pc**2")
u5 = Unit("Msun * s")
u6 = u4 * u5
assert u6.expr == pc_sym**2 * msun_sym * s_sym
assert_allclose_units(u6.base_value, pc_mks**2 * msun_mks, 1e-12)
assert u6.dimensions == length**2 * mass * time
def test_base_equivalent():
"""
Check base equivalent of a unit.
"""
Msun_mks = mass_sun_kg
Mpc_mks = m_per_mpc
u1 = Unit("Msun * Mpc**-3")
u2 = Unit("kg * m**-3")
u3 = u1.get_base_equivalent()
assert u2.expr == u3.expr
assert u2 == u3
assert_allclose_units(u1.base_value, Msun_mks / Mpc_mks**3, 1e-12)
assert u2.base_value == 1
assert u3.base_value == 1
mass_density = mass / length**3
assert u1.dimensions == mass_density
assert u2.dimensions == mass_density
assert u3.dimensions == mass_density
assert_allclose_units(
u1.get_conversion_factor(u3)[0], Msun_mks / Mpc_mks**3, 1e-12)
with pytest.raises(UnitConversionError):
u1.get_conversion_factor(Unit('m'))
with pytest.raises(UnitConversionError):
u1.get_conversion_factor(Unit('degF'))
def test_create_from_expr():
"""
Create units from sympy Exprs and check attributes.
"""
pc_mks = m_per_pc
yr_mks = sec_per_year
# Symbol expr
s1 = Symbol("pc", positive=True)
s2 = Symbol("yr", positive=True)
# Mul expr
s3 = s1 * s2
# Pow expr
s4 = s1**2 * s2**(-1)
u1 = Unit(s1)
u2 = Unit(s2)
u3 = Unit(s3)
u4 = Unit(s4)
assert u1.expr == s1
assert u2.expr == s2
assert u3.expr == s3
assert u4.expr == s4
assert_allclose_units(u1.base_value, pc_mks, 1e-12)
assert_allclose_units(u2.base_value, yr_mks, 1e-12)
assert_allclose_units(u3.base_value, pc_mks * yr_mks, 1e-12)
assert_allclose_units(u4.base_value, pc_mks**2 / yr_mks, 1e-12)
assert u1.dimensions == length
assert u2.dimensions == time
assert u3.dimensions == length * time
assert u4.dimensions == length**2 / time
def test_create_with_duplicate_dimensions():
"""
Create units with overlapping dimensions. Ex: km/Mpc.
"""
u1 = Unit("J * s**-1")
u2 = Unit("km/s/Mpc")
km_mks = m_per_km
Mpc_mks = m_per_mpc
assert u1.base_value == 1
assert u1.dimensions == power
assert_allclose_units(u2.base_value, km_mks / Mpc_mks, 1e-12)
assert u2.dimensions == rate
def test_base_equivalent():
"""
Check base equivalent of a unit.
"""
Msun_mks = mass_sun_kg
Mpc_mks = m_per_mpc
u1 = Unit("Msun * Mpc**-3")
u2 = Unit("kg * m**-3")
u3 = u1.get_base_equivalent()
assert u2.expr == u3.expr
assert u2 == u3
assert_allclose_units(u1.base_value, Msun_mks / Mpc_mks ** 3, 1e-12)
assert u2.base_value == 1
assert u3.base_value == 1
mass_density = mass / length ** 3
assert u1.dimensions == mass_density
assert u2.dimensions == mass_density
assert u3.dimensions == mass_density
assert_allclose_units(
u1.get_conversion_factor(u3)[0], Msun_mks / Mpc_mks ** 3, 1e-12
)
with pytest.raises(UnitConversionError):
u1.get_conversion_factor(Unit("m"))
with pytest.raises(UnitConversionError):
u1.get_conversion_factor(Unit("degF"))
reg = UnitRegistry(unit_system=cgs_unit_system)
u = Unit("kg", registry=reg)
assert u.get_base_equivalent() == Unit("g")
u = Unit("kg")
assert u.get_base_equivalent() == Unit("kg")
u = Unit("A")
assert u.get_base_equivalent(unit_system="mks") == Unit("A")
def test_power():
"""
Take units to some power.
"""
from sympy import nsimplify
pc_mks = m_per_pc
mK_mks = 1e-3
u1_dims = mass * length**2 * time**-3 * temperature**4
u1 = Unit("kg * pc**2 * s**-3 * mK**4")
u2 = u1**2
assert u2.dimensions == u1_dims**2
assert_allclose_units(u2.base_value, (pc_mks**2 * mK_mks**4)**2, 1e-12)
u3 = u1**(-1.0 / 3)
assert u3.dimensions == nsimplify(u1_dims**(-1.0 / 3))
assert_allclose_units(u3.base_value, (pc_mks**2 * mK_mks**4)**(-1.0 / 3),
1e-12)
def test_division():
"""
Divide two units.
"""
pc_mks = m_per_pc
km_mks = m_per_km
# Create symbols
pc_sym = Symbol("pc", positive=True)
km_sym = Symbol("km", positive=True)
s_sym = Symbol("s", positive=True)
# Create units
u1 = Unit("pc")
u2 = Unit("km * s")
u3 = u1 / u2
assert u3.expr == pc_sym / (km_sym * s_sym)
assert_allclose_units(u3.base_value, pc_mks / km_mks, 1e-12)
assert u3.dimensions == 1 / time
