BUG-25061 use local na_rep variable

Author: JustinZhengBC

pandas/io/formats/format.py

@@ -1063,21 +1063,23 @@ def format_values_with(float_format):
             # default formatter leaves a space to the left when formatting
             # floats, must be consistent for left-justifying NaNs (GH #25061)
             if self.justify == 'left':
-                self.na_rep = ' ' + self.na_rep
+                na_rep = ' ' + self.na_rep
+            else:
+                na_rep = self.na_rep
 
             # separate the wheat from the chaff
             values = self.values
             mask = isna(values)
             if hasattr(values, 'to_dense'):  # sparse numpy ndarray
                 values = values.to_dense()
             values = np.array(values, dtype='object')
-            values[mask] = self.na_rep
+            values[mask] = na_rep
             imask = (~mask).ravel()
             values.flat[imask] = np.array([formatter(val)
                                            for val in values.ravel()[imask]])
 
             if self.fixed_width:
-                return _trim_zeros(values, self.na_rep)
+                return _trim_zeros(values, na_rep)
 
             return values