feat: add kg_to_lbs and lbs_to_kg conversions (#13)

fixit/cli.py

@@ -12,7 +12,9 @@
 CONVERSIONS = {
     "c2f": convert.celsius_to_fahrenheit,
     "f2c": convert.fahrenheit_to_celsius,
+    "kg2lb": convert.kg_to_lbs,
     "km2mi": convert.km_to_miles,
+    "lb2kg": convert.lbs_to_kg,
     "mi2km": convert.miles_to_km,
 }
 

fixit/convert.py

@@ -1,6 +1,7 @@
 """Unit conversions."""
 
 KM_PER_MILE = 1.609344
+LBS_PER_KG = 2.20462
 
 
 def celsius_to_fahrenheit(c: float) -> float:
@@ -37,3 +38,22 @@ def miles_to_km(miles: float) -> float:
         miles_to_km(1) returns approximately 1.6093.
     """
     return miles * KM_PER_MILE
+
+
+def kg_to_lbs(kg: float) -> float:
+    """Convert kilograms to pounds.
+
+    Example:
+        kg_to_lbs(1) returns approximately 2.20462.
+    """
+    return kg * LBS_PER_KG
+
+
+def lbs_to_kg(lbs: float) -> float:
+    """Convert pounds to kilograms.
+
+    Example:
+        lbs_to_kg(2.20462) returns approximately 1.0.
+    """
+    return lbs / LBS_PER_KG
+

tests/test_cli.py

@@ -1,3 +1,5 @@
+import pytest
+
 from fixit.cli import main
 
 
@@ -43,3 +45,14 @@ def test_top_words_command_defaults_to_three(capsys):
 
     assert result == 0
     assert capsys.readouterr().out == "one: 1\ntwo: 1\nthree: 1\n"
+
+
+def test_convert_command_weight(capsys):
+    result = main(["convert", "1", "kg2lb"])
+    assert result == 0
+    assert float(capsys.readouterr().out.strip()) == pytest.approx(2.20462)
+
+    result = main(["convert", "2.20462", "lb2kg"])
+    assert result == 0
+    assert float(capsys.readouterr().out.strip()) == pytest.approx(1.0)
+

tests/test_convert.py

@@ -3,7 +3,9 @@
 from fixit.convert import (
     celsius_to_fahrenheit,
     fahrenheit_to_celsius,
+    kg_to_lbs,
     km_to_miles,
+    lbs_to_kg,
     miles_to_km,
 )
 
@@ -38,3 +40,14 @@ def test_absolute_zero():
 
 def test_float_km_to_miles():
     assert km_to_miles(1.5) == pytest.approx(0.932056788)
+
+
+def test_kg_to_lbs():
+    assert kg_to_lbs(1) == pytest.approx(2.20462)
+    assert kg_to_lbs(10) == pytest.approx(22.0462)
+
+
+def test_lbs_to_kg():
+    assert lbs_to_kg(2.20462) == pytest.approx(1.0)
+    assert lbs_to_kg(10) == pytest.approx(4.53592, rel=1e-3)
+