u

Statically typed units.

Quickstart

Type safe assignments:

duration: u.Duration = u.seconds(5)  # Ok
distance: u.Distance = u.amperes(5)  # Type checking error

Type safe math:

print(u.seconds(120) + u.minutes(3))  # Ok
print(u.seconds(120) + u.amperes(3))  # Type checking error

Type safe derived units:

SPEED = u.DIV[u.DISTANCE, u.DURATION]
Speed = u.Quantity[SPEED]

speed: Speed = u.km(5) / u.hours(1)  # Ok
speed: Speed = (u.km / u.hours)(5)  # Also ok

ELECTRIC_CHARGE = u.MUL[u.DURATION, u.ELECTRIC_CURRENT]
ElectricCharge = u.Quantity[ELECTRIC_CHARGE]

charge: ElectricCharge = u.sec(3) * u.amperes(2)  # Ok
charge: ElectricCharge = u.amperes(2) * u.sec(3)  # Also ok

Reusable prefixes:

print(u.megabytes(5) == u.mega(u.bytes)(5))  # True

Define your own quantities and units:

class TASTINESS(u.QUANTITY):
    pass

Tastiness = u.Quantity[TASTINESS]

mmm = u.Unit(Tastiness, symbol='mmm', multiplier=1)
yum = u.Unit(Tastiness, 'yum', 10)

taste: Tastiness = yum(42)

Convert to string:

thousand_meters = u.meters(1000)
print(thousand_meters)             # Automatically selects a suitable unit: "1 km"
print(f'{thousand_meters:m}')      # Uses the specified unit: "1000 m"
print(f'{thousand_meters:cm:m}')   # Selects a unit from the given range: "1000 m"
print(f'{thousand_meters:.1f m}')  # Formats the number: "1000.0 m"

Caveats

Since type checkers don't understand math, calculations involving different types of quantities sometimes cause type checkers to complain even though they're correct. For example:

area: u.Area = (u.m2 * u.kelvins / u.kelvins)(1)  # Type checking error

Documentation

There is no online documentation, but everything has docstrings and type annotations. Your IDE should be able to show you all the relevant information.