Introduction to SciMath Units¶
A large number of units used in science and engineering are available for use, and scimath.units makes working with and converting among them easy.
We can import unit objects from the scimath.units submodules. (See list of available units for a listing by submodule.) There are submodules for many categories of physical quantities.
>>> from scimath.units.length import foot, inch, meter >>> 3 * foot 0.9144000000000001*m >>> foot / inch 12.0 >>> foot / meter 0.3048
Unit objects display natively in SI fundamental units and can be used to generate unit conversion factors or to see how units relate to one another.
>>> from scimath.units.pressure import pascal >>> pascal * meter ** 2 1.0*m*kg*s**-2
Caution: If you are using this tool to produce conversion factors, remember
that the factor is the inverse of what it looks like. Above, we divided one
foot by one meter to get the ratio 0.3048. That is,
foot / meter yields the
number of meters per foot. Be careful to think through the logic clearly when
developing conversion factors.
You can define your own arbitrary units and use them for calculating conversion factors:
>>> from scimath.units.length import inch >>> from scimath.units.force import lbf >>> from scimath.units.pressure import torr >>> my_psi = 2 * lbf / inch ** 2 >>> my_psi / torr 103.44718363855331
Internally, they are stored as a derivation of fundamental physical quantities expressed in the SI system
>>> my_psi 13789.509579019157*m**-1*kg*s**-2
Conversions can be made between units with the same derivation using
>>> from scimath.units.api import convert >>> from scimath.units.force import lbf, newton >>> convert(1, lbf, newton) 4.44822
However, adding incompatible units raises an
>>> from scimath.units.electromagnetism import volt >>> from scimath.units.mass import kilogram >>> 1 * volt + 2 * kilogram Traceback (most recent call last): File "<stdin>", line 1, in <module> File "scimath/units/unit.py", line 62, in __add__ raise IncompatibleUnits("add", self, other) scimath.units.unit.IncompatibleUnits: Cannot add quanitites with units of 'm**2*kg*s**-3*A**-1' and 'kg'