UnitPy (Unit Python)

UnitPy is a Python package for defining, converting, and working with units.

The goal of the package is to be simple, straightforward, and performant.

This package directly implements NIST (National Institute of Standards and Technology) official unit definitions.

Installation

Pip installable package:

pip install unitpy

pypi: unitpy

Requirements / Dependencies

Python 3.7 and up

Basic Usage

Defining Unit

from unitpy import U, Q, Unit, Quantity
# U = Unit

u = Unit("kilometer")
u = U("kilometer")
u = U("km")
u = U.kilometer
u = U.km

u = U("kilometer/hour")
u = U("km/h")
u = U.kilometer / U.hour
u = U.km / U.h

# properties
print(u.dimensionality)  # [length] / [time]
print(u.dimensionless)   # False
print(u.base_unit)       # meter / second

Defining Quantity

** Quantity = Value + Unit **

from unitpy import U, Q , Unit, Quantity
# Q = Quantity

q = 1 * U("kilometer/hour") 
q = 1 * (U.kilometer / U.hour)
q = Quantity("1 km/h")
q = Q("1 kilometer per hour")
q = Q("1*kilometer/hour")


# properties
print(q.unit)            # kilometer / hour
print(q.dimensionality)  # [length] / [time]
print(q.dimensionless)   # False
print(q.base_unit)       # meter / second

Unit Conversion

from unitpy import U, Q , Unit, Quantity
# Q = Quantity

q = 1 * U("km/h") 
q2 = q.to("mile per hour")
print(q2)  # 0.6213711922 mile / hour

Mathematical operation

from unitpy import U, Q 

q = 1 * U("km/h") 
q2 = 2.2 * U("mile per hour")
print(q2 + q)                 # 2.8213711923 mile / hour
print(q2 - q)                 # 1.5786288077 mile / hour
print(q2 * q)                 # 2.2 kilometer mile / hour**2
print(q2 / q)                 # 2.2 mile / kilometer
print((q2 / q).dimensionless) # True

Temperature

Abbreviations:

• fahrenheits: degF
• celsius: degC
• kelvin: degK, K
• rankine: degR

from unitpy import U, Q

q = 300 * U("K")
q2 = 200 * U("K")

print(q + q2)        # 500.0 kelvin
print(q.to("degC"))  # 26.85 Celsius
print(q.to("degF"))  # 830.6344444444 Fahrenheit
print(q.to("degR"))  # 166.6666666667 Rankine

Temperature units are non-multiplicative units. They are expressed with respect to a reference point (offset).

degC = 5/9 * (degF - 32)

Default behavior is absolute units.

For relative units use dedicated functions add_rel() or sub_rel().

from unitpy import U, Q

q = 10 * U("degC")
q2 = 5 * U("degC")

# absolute
print(q.to("K"))         # 283.15 kelvin
print(q + q2)            # 288.15 Celsius 
print((q + q2).to("K"))  # 561.3 kelvin
print(q - q2)            # -268.15 Celsius
print((q - q2).to("K"))  # 5.0 kelvin

# relative
print(q.add_rel(q2))      # 15 Celsius
print(q.sub_rel(q2))      # 5 Celsius
print(abs(-10 * U.degC))  # 10 Celsius

Notes

• this package utilizes the American spellings "meter," "liter," and "ton"