Comparisons and hashing

Quantities can be compared as long as they have the same dimension. Comparisons automatically handle unit conversion.

from quantium import u

speed_1 = 100 * u.km / u.h
speed_2 = 30 * u.m / u.s

print(speed_1 == speed_2) # False
print(speed_1 < speed_2)  # True (100 km/h is ~27.8 m/s)
print(speed_2 > speed_1)  # True

Floating point noise

The Quantity equality uses math.isclose to provide fuzzy equality. This means small floating-point noise won’t break comparisons:

q1 = 1.0 * u.m
q2 = (1.0 + 1e-13) * u.m
print(q1 == q2) # True

Hashing and as_key()

Because equality is fuzzy, Quantity objects are not hashable by default (doing so would break the hash/equality contract). Use .as_key() to create a stable, hashable representation if you need to use quantities as dictionary keys or in sets.

q1 = (1.0 + 1e-13) * u.m
q2 = 1.0 * u.m

print(q1 == q2) # True

# Use as_key to create a stable, hashable key
safe_dict = {}
safe_dict[q1.as_key()] = "value"
print(safe_dict[q2.as_key()])  # "value"