add case for negative exponent truncation, add guard for the mantissa

Author: adrianmolzon

bayes_opt/logger.py

@@ -97,7 +97,8 @@ def _format_number(self, x: float) -> str:
                 if width > 0:
                     result += s[dot_pos : dot_pos + width]
             else:
-                result += s[:width]
+                head = s[:e_pos] if "e" in s else s
+                result += head[:width]
             if "e" in s:
                 result += end
             result = result.ljust(self._default_cell_size)

tests/test_logger.py

@@ -91,7 +91,10 @@ def test_format_number():
     formatted = logger._format_number(sci_float)
     assert formatted == "1.111e-05"
 
-    # Test negative scientific notation truncation
+    sci_float_neg = -1.11111111e-5
+    formatted = logger._format_number(sci_float_neg)
+    assert formatted == "-1.11e-05"
+
     sci_float = -12345678901234.5678901234
     formatted = logger._format_number(sci_float)
     assert len(formatted) == logger._default_cell_size