# Units¶

WrightTools provides its own units system. You can use it directly, if you wish.

>>> import WrightTools as wt
>>> wt.units.convert(2., 'eV', 'nm')
619.9209921660013


Under the hood, the WrightTools units system is backed by a Pint <https://pint.readthedocs.io unit registry. This registry has all of the units in the default Pint registry, plus a few added by WrightTools (including some extra aliases of pint units for backwards compatibility with older WrightTools). Additionally this unit registry automatically enables the spectroscopy context as well as a custom context for handling delay behavior (which inserts a factor of 2 as delays typically increase the path of light by two times their physical movement).

The pint unit registry can be directly accessed at wt.units.ureg.

To query whether a specific conversion is applicable, you can use wt.units.is_valid_conversion(). To get a list of commonly used units that are valid conversions, you can use wt.units.get_valid_conversions().

This same units system enables the units-aware properties throughout WrightTools.

The units system also provides a symbol for many units, enabling easy plotting. You can get the symbol using wt.units.get_symbol().

The following table contains units commonly used in WrightTools, though many others (including compound units) may be used if desired.

 name description symbol rad radian $$\omega$$ deg degrees $$\omega$$ fs femtoseconds $$\tau$$ ps picoseconds $$\tau$$ ns nanoseconds $$\tau$$ nm nanometers $$\lambda$$ wn wavenumbers $$\bar{\nu}$$ eV electronvolts $$\hslash\omega$$ meV millielectronvolts $$\hslash\omega$$ Hz hertz $$f$$ THz terahertz $$f$$ GHz gigahertz $$f$$ K kelvin $$T$$ deg_C celsius $$T$$ deg_F fahrenheit $$T$$ mOD mOD None OD OD None nm_p nanometers None um microns $$\lambda$$ mm millimeters $$\lambda$$ cm centimeters $$\lambda$$ in inches $$\lambda$$ fs_t femtoseconds $$\tau$$ ps_t picoseconds $$\tau$$ ns_t nanoseconds $$\tau$$ us_t microseconds $$\tau$$ ms_t milliseconds $$\tau$$ s_t seconds $$\tau$$ m_t minutes $$\tau$$ h_t hours $$\tau$$ d_t days $$\tau$$