Quantity value
The term ‘quantity value’ refers to a measured value paired with the unit of measurement. QV
provides several functions in the quantity_value
module that support the notion of quantity values:
More information is given in the Examples section.
- qratio(value_unit_1, value_unit_2, unit=None)
Return a quantity value for
value_unit_1/value_unit_2
. If the signature of the associated units are in simplified form, signature information is retained in the quotient.When
unit
is None, the reference unit is used.Example
>>> context = Context( ("Current","I"),("Voltage","V") ) >>> ureg = UnitRegister("ureg",context) >>> volt = ureg.unit( RatioScale(context['Voltage'],'volt','V') ) >>> voltage_ratio = context.declare('voltage_ratio','V/V','Voltage//Voltage') >>> volt_per_volt = ureg.unit( RatioScale(context['voltage_ratio'],'volt_per_volt','V/V') ) >>> v1 = qvalue(1.23, volt) >>> v2 = qvalue(9.51, volt) >>> qratio( v2,v1 ) qvalue(7.73170731...,volt_per_volt)
- qresult(value_unit, unit=None, simplify=True, value_result=<function <lambda>>, *arg, **kwarg)
Return a
qvalue
.value_unit
is a quantity-value or expression of quantity-values.If a
unit
is supplied, it is used to report the measure. If not, the measure is reported in the reference unit for that quantity.If
simplify
isTrue
, unit signatures will be simplified.The function
value_result
is applied to the value as a final processing step.Example
>>> context = Context( ("Length","L"), ("Time","T") ) >>> Speed = context.declare('Speed','V','Length/Time') >>> si = UnitRegister("si",context) >>> metre = si.unit( RatioScale(context['Length'],'metre','m') ) >>> second = si.unit( RatioScale(context['Time'],'second','s') ) >>> metre_per_second = si.unit( RatioScale(context['Speed'],'metre_per_second','m*s-1') ) >>> d = qvalue(0.5,metre) >>> t = qvalue(1.0,second) >>> v0 = qresult(d/t) >>> print( "average speed =", v0 ) average speed = 0.5 m*s-1 >>> x0 = qvalue(.3,metre) >>> print( "displacement =", x0 + v0*t ) displacement = 0.8 m
- qvalue(value, unit)
Create a new quantity value object.
value
is the measure,unit
is the measurement scaleExample
>>> context = Context( ("Length","L"), ("Time","T") ) >>> si = UnitRegister("si",context) >>> metre = si.unit( RatioScale(context['Length'],'metre','m') ) >>> qvalue( 1.84, metre ) qvalue(1.84,metre)
- unit(quantity_value)
Return the unit (measurement scale)
- value(quantity_value)
Return the value