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fix(units): stop aliasing C to degree Celsius #672

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fix(units): stop aliasing C to degree Celsius #672

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20d5291
test(units): expect the symbol C to stay coulomb
Cherith1222 Oct 18, 2026
5aa83c0
fix(units): stop aliasing C to degree Celsius
Cherith1222 Oct 18, 2026
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10 changes: 9 additions & 1 deletion cf_xarray/tests/test_units.py
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,7 @@
Copyright (c) 2017 MetPy Developers.
"""

import numpy as np
import pytest

pytest.importorskip("pint")
Expand Down Expand Up @@ -90,7 +91,14 @@ def test_udunits_format(units, expected):

@pytest.mark.parametrize(
"alias",
[ureg("Celsius"), ureg("degC"), ureg("C"), ureg("deg_C"), ureg("degrees_Celsius")],
[ureg("Celsius"), ureg("degC"), ureg("deg_C"), ureg("degrees_Celsius")],
)
def test_temperature_aliases(alias):
assert alias == ureg("celsius")


def test_coulomb_symbol_survives_cf_units():
assert ureg("C") == ureg("coulomb")
speed = np.sqrt(100 * ureg.eV / ureg.m_e).to("km/s")
assert speed.units == ureg("km/s")
assert speed.magnitude == pytest.approx(4193.828809546234)
2 changes: 1 addition & 1 deletion cf_xarray/units.py
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Original file line number Diff line number Diff line change
Expand Up @@ -92,7 +92,7 @@ def short_formatter(unit, registry, **options):
units.define("year = 365.25 * day = yr")

# Define commonly encountered units not defined by pint
units.define("@alias degC = C = deg_C = Celsius = degrees_Celsius")
units.define("@alias degC = deg_C = Celsius = degrees_Celsius")
units.define("@alias degK = deg_K")
units.define("@alias day = d")
units.define("@alias hour = h") # Not the Planck constant...
Expand Down