Merge pull request #34 from terrycojones/catch-index-error

Avert an IndexError when a totally non-numeric value is passed to EngNumber

Author: slightlynybbled

engineering_notation/eng_notation.py

@@ -2,8 +2,6 @@
 
 from decimal import Decimal
 import re
-from string import digits
-import sys
 from types import NotImplementedType
 
 from typing import Self
@@ -465,7 +463,8 @@ def __init__(
 
         Raises:
             TypeError: If the value type is unsupported.
-            ValueError: If a string value cannot be parsed by Decimal.
+            ValueError: If a string value cannot be parsed by Decimal or has no
+                numeric part.
         """
         self.precision = 2 if precision is None else precision
         self._precision_explicit = precision is not None
@@ -474,6 +473,12 @@ def __init__(
 
         if isinstance(value, str):
             numeric_part, _ = _split_value_and_unit(value)
+
+            if not numeric_part:
+                # Raise a value error to avoid the IndexError that would otherwise
+                # occur (due to numeric_part[-1]) if numeric_part is empty.
+                raise ValueError(f"Value {value!r} has no numeric part.")
+
             for suffix in _suffix_keys:
                 if suffix == numeric_part[-1]:
                     numeric_part = numeric_part[:-1] + _suffix_lookup[suffix]

tests/test_engnum.py

@@ -646,3 +646,10 @@ def test_to_float():
     # negative_numbers
     assert float(EngUnit("-220k")) == -220000.0
     assert float(EngUnit("-220m")) == -0.220
+
+
+def test_value_error():
+    # Unconvertible values.
+
+    with pytest.raises(ValueError):
+        EngUnit("XXX")