def unitsAreConsistent(expr, targetUnits=None):
"""Check if an expression's units are compatible.
If `targetUnits` provided, also checks for compatibility for
converting to `targetUnits`.
Raises UnitMisMatchError when applicable.
Notes:
If `targetUnits` is a units.Dimension, requires `expr` to
evaluate to units with same units.Dimension (eg. must include units in `expr`)
If `expr` has dimension of `1` (unit-less), returns `True`
barring other errors or targetUnits being units.Dimension.
:param expr: sympy.Expr
:param targetUnits: str\\units.Quantity\\units.Dimension
:return: True or raises UnitMisMatchError
"""
logger.log(logging.DEBUG - 1, f'unitsAreConsistent({expr}, {targetUnits})')
try:
# rough check within expression
check_dimensions(expr)
logger.log(logging.DEBUG - 1,
f"check_dimensions -> {bool(check_dimensions(expr))}")
except ValueError as e:
raise UnitMisMatchError(repr(e))
except TypeError as e:
raise UnitMisMatchError(repr(e))
expr_dim = getDimension(expr)
logger.log(logging.DEBUG - 1, f"expr_dim = {expr_dim}")
if expr_dim is None:
raise UnitMisMatchError("Dimension could not be determined")
if targetUnits is None:
return True
# get dimensions of target units
if isinstance(targetUnits, str):
try:
targetUnits = unitSubs[targetUnits]
except KeyError:
targetUnits = parseUnits(targetUnits)
target_dim = getDimension(targetUnits)
logger.log(logging.DEBUG - 1, f"target_dim = {target_dim}")
if isinstance(targetUnits, units.Dimension):
if targetUnits.name == expr_dim.name:
return True
else:
raise UnitMisMatchError(
f"{expr_dim} is not specified {target_dim}")
# compare dimensions
if expr_dim.name == 1 or expr_dim.name == target_dim.name:
return True
else:
raise UnitMisMatchError(f"{expr_dim} incompatible with {target_dim}")
def test_check_dimensions():
x = symbols('x')
assert check_dimensions(inch + x) == inch + x
assert check_dimensions(length + x) == length + x
# after subs we get 2*length; check will clear the constant
assert check_dimensions((length + x).subs(x, length)) == length
assert check_dimensions(newton * meter + joule) == joule + meter * newton
raises(ValueError, lambda: check_dimensions(inch + 1))
raises(ValueError, lambda: check_dimensions(length + 1))
raises(ValueError, lambda: check_dimensions(length + time))
raises(ValueError, lambda: check_dimensions(meter + second))
raises(ValueError, lambda: check_dimensions(2 * meter + second))
raises(ValueError, lambda: check_dimensions(2 * meter + 3 * second))
raises(ValueError, lambda: check_dimensions(1 / second + 1 / meter))
raises(ValueError, lambda: check_dimensions(2 * meter *
(mile + centimeter) + km))
def test_check_dimensions():
x = symbols('x')
assert check_dimensions(inch + x) == inch + x
assert check_dimensions(length + x) == length + x
# after subs we get 2*length; check will clear the constant
assert check_dimensions((length + x).subs(x, length)) == length
raises(ValueError, lambda: check_dimensions(inch + 1))
raises(ValueError, lambda: check_dimensions(length + 1))
raises(ValueError, lambda: check_dimensions(length + time))
raises(ValueError, lambda: check_dimensions(meter + second))
raises(ValueError, lambda: check_dimensions(2 * meter + second))
raises(ValueError, lambda: check_dimensions(2 * meter + 3 * second))
raises(ValueError, lambda: check_dimensions(1 / second + 1 / meter))
raises(ValueError, lambda: check_dimensions(2 * meter*(mile + centimeter) + km))