diff --git a/python/lsst/pex/config/history.py b/python/lsst/pex/config/history.py
index 2800f7d..6a1e77b 100644
--- a/python/lsst/pex/config/history.py
+++ b/python/lsst/pex/config/history.py
@@ -214,7 +214,7 @@ def format(config, name=None, writeSourceLine=True, prefix="", verbose=False):
             if writeSourceLine:
                 line.append(
                     [
-                        "%s" % ("%s:%d" % (frame.filename, frame.lineno)),
+                        f"{frame.filename}:{frame.lineno}",
                         "FILE",
                     ]
                 )
@@ -252,14 +252,14 @@ def format(config, name=None, writeSourceLine=True, prefix="", verbose=False):
     fullname = f"{config._name}.{name}" if config._name is not None else name
     msg.append(_colorize(re.sub(r"^root\.", "", fullname), "NAME"))
     for value, output in outputs:
-        line = prefix + _colorize("%-*s" % (valueLength, value), "VALUE") + " "
+        line = prefix + _colorize(f"{value:<{valueLength}}", "VALUE") + " "
         for i, vt in enumerate(output):
             if writeSourceLine:
-                vt[0][0] = "%-*s" % (sourceLength, vt[0][0])
+                vt[0][0] = f"{vt[0][0]:<{sourceLength}}"
 
             output[i] = " ".join([_colorize(v, t) for v, t in vt])
 
-        line += ("\n%*s" % (valueLength + 1, "")).join(output)
+        line += ("\n" + f"{'':>{valueLength + 1}}").join(output)
         msg.append(line)
 
     return "\n".join(msg)
diff --git a/python/lsst/pex/config/listField.py b/python/lsst/pex/config/listField.py
index 2117bb0..809c6d2 100644
--- a/python/lsst/pex/config/listField.py
+++ b/python/lsst/pex/config/listField.py
@@ -115,16 +115,14 @@ def validateItem(self, i, x):
             `ListField.itemCheck` method.
         """
         if not isinstance(x, self._field.itemtype) and x is not None:
-            msg = "Item at position %d with value %s is of incorrect type %s. Expected %s" % (
-                i,
-                x,
-                _typeStr(x),
-                _typeStr(self._field.itemtype),
+            msg = (
+                f"Item at position {i} with value {x} is of incorrect type {_typeStr(x)}. "
+                f"Expected {_typeStr(self._field.itemtype)}"
             )
             raise FieldValidationError(self._field, self._config, msg)
 
         if self._field.itemCheck is not None and not self._field.itemCheck(x):
-            msg = "Item at position %d is not a valid value: %s" % (i, x)
+            msg = f"Item at position {i} is not a valid value: {x}"
             raise FieldValidationError(self._field, self._config, msg)
 
     def list(self):
@@ -329,15 +327,15 @@ def __init__(
             raise ValueError(f"Unsupported dtype {_typeStr(dtype)}")
         if length is not None:
             if length <= 0:
-                raise ValueError("'length' (%d) must be positive" % length)
+                raise ValueError(f"'length' ({length}) must be positive")
             minLength = None
             maxLength = None
         else:
             if maxLength is not None and maxLength <= 0:
-                raise ValueError("'maxLength' (%d) must be positive" % maxLength)
+                raise ValueError(f"'maxLength' ({maxLength}) must be positive")
             if minLength is not None and maxLength is not None and minLength > maxLength:
                 raise ValueError(
-                    "'maxLength' (%d) must be at least as large as 'minLength' (%d)" % (maxLength, minLength)
+                    f"'maxLength' ({maxLength}) must be at least as large as 'minLength' ({minLength})"
                 )
 
         if listCheck is not None and not hasattr(listCheck, "__call__"):
@@ -412,13 +410,13 @@ def validate(self, instance):
         if value is not None:
             lenValue = len(value)
             if self.length is not None and not lenValue == self.length:
-                msg = "Required list length=%d, got length=%d" % (self.length, lenValue)
+                msg = f"Required list length={self.length}, got length={lenValue}"
                 raise FieldValidationError(self, instance, msg)
             elif self.minLength is not None and lenValue < self.minLength:
-                msg = "Minimum allowed list length=%d, got length=%d" % (self.minLength, lenValue)
+                msg = f"Minimum allowed list length={self.minLength}, got length={lenValue}"
                 raise FieldValidationError(self, instance, msg)
             elif self.maxLength is not None and lenValue > self.maxLength:
-                msg = "Maximum allowed list length=%d, got length=%d" % (self.maxLength, lenValue)
+                msg = f"Maximum allowed list length={self.maxLength}, got length={lenValue}"
                 raise FieldValidationError(self, instance, msg)
             elif self.listCheck is not None and not self.listCheck(value):
                 msg = f"{value} is not a valid value"
@@ -510,8 +508,9 @@ def _compare(self, instance1, instance2, shortcut, rtol, atol, output):
         equal = True
         for n, v1, v2 in zip(range(len(l1)), l1, l2):
             result = compareScalars(
-                "%s[%d]" % (name, n), v1, v2, dtype=self.dtype, rtol=rtol, atol=atol, output=output
+                f"{name}[{n}]", v1, v2, dtype=self.dtype, rtol=rtol, atol=atol, output=output
             )
+
             if not result and shortcut:
                 return False
             equal = equal and result