Fix precision bug

Author: slightlynybbled

engineering_notation/eng_notation.py

@@ -97,7 +97,7 @@ class EngUnit:
     def __init__(
         self,
         value: str | int | float | EngNumber | EngUnit,
-        precision: int = 2,
+        precision: int | None = None,
         significant: int = 0,
         unit: str | None = None,
         separator: str = "",
@@ -108,6 +108,7 @@ def __init__(
         Args:
             value: String, int, float, or EngNumber value to parse.
             precision: Decimal places used when significant is 0.
+                Defaults to 2 when None.
             significant: Significant digits; takes precedence over precision.
             unit: Explicit unit suffix. If None, a unit suffix is parsed from
                 the end of a string value when present.
@@ -448,7 +449,7 @@ class EngNumber:
     def __init__(
         self,
         value: str | int | float | EngNumber,
-        precision: int = 2,
+        precision: int | None = None,
         significant: int = 0,
         separator: str = "",
     ) -> None:
@@ -458,14 +459,16 @@ def __init__(
         Args:
             value: String, int, float, or EngNumber value to parse.
             precision: Decimal places used when significant is 0.
+                Defaults to 2 when None.
             significant: Significant digits; takes precedence over precision.
             separator: String inserted between the numeric value and suffix.
 
         Raises:
             TypeError: If the value type is unsupported.
             ValueError: If a string value cannot be parsed by Decimal.
         """
-        self.precision = precision
+        self.precision = 2 if precision is None else precision
+        self._precision_explicit = precision is not None
         self.significant = significant
         self.separator = separator
 
@@ -560,7 +563,11 @@ def __repr__(self) -> str:
             base = base.rstrip(".")
 
         # remove trailing .00 in precision 2
-        if self.precision == 2 and self.significant == 0:
+        if (
+            self.precision == 2
+            and self.significant == 0
+            and not self._precision_explicit
+        ):
             if ".00" in base:
                 base = base[:-3]
 

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "engineering-notation"
-version = "0.13.1"
+version = "0.13.2"
 description = "Easy engineering notation"
 readme = "readme.md"
 requires-python = ">=3.12"

tests/test_engnum.py

@@ -71,6 +71,20 @@ def test_engnum_significant():
     assert str(EngNumber("2.22m", significant=3)) == "2.22m"
 
 
+def test_engnum_precision_rounding():
+    assert str(EngNumber("1.234k", precision=1)) == "1.2k"
+    assert str(EngNumber("1.234k", precision=3)) == "1.234k"
+    assert str(EngNumber("1.2k", precision=0)) == "1k"
+    assert str(EngNumber("-1.234k", precision=1)) == "-1.2k"
+    assert str(EngNumber("1.666666", precision=2)) == "1.67"
+
+
+def test_engnum_precision_trailing_zeros():
+    assert str(EngNumber("1k", precision=2)) == "1.00k"
+    assert str(EngNumber("1k", precision=3)) == "1.000k"
+    assert str(EngNumber("2.0", precision=2)) == "2.00"
+
+
 def test_engnum_separator():
     assert str(EngNumber("1.23k", separator=" ")) == "1.23 k"
     assert str(EngNumber("1.23k", separator=" ").to_pn()) == "1k23"
@@ -366,6 +380,12 @@ def test_to_str():
     assert EngUnit("2m", unit="meter").eng_num == EngNumber("2m")
 
 
+def test_engunit_precision():
+    assert str(EngUnit("1.234kHz", precision=1)) == "1.2kHz"
+    assert str(EngUnit("1kHz", precision=3)) == "1.000kHz"
+    assert str(EngUnit("-1.234kHz", precision=1)) == "-1.2kHz"
+
+
 def test_to_str_large():
     # positive_numbers
     assert str(EngUnit("220kHz")) == "220kHz"