Changing SIfloat to only convert last character of the string

pykat/SIfloat.py

 import os
 import re
+import pykat.exceptions as pkex
 
-#staticmethod
+__suffix = {'y': 'e-24',  # yocto
+            'z': 'e-21',  # zepto
+            'a': 'e-18',  # atto
+            'f': 'e-15',  # femto
+            'p': 'e-12',  # pico
+            'n': 'e-9',   # nano
+            'u': 'e-6',   # micro
+            'm': 'e-3',   # mili
+            'c': 'e-2',   # centi
+            'd': 'e-1',   # deci
+            'k': 'e3',    # kilo
+            'M': 'e6',    # mega
+            'G': 'e9',    # giga
+            'T': 'e12',   # tera
+            'P': 'e15'   # peta
+            }
+            
 def SIfloat(value):
     if value==None: 
         return value
+    
     if type(value)==list:
         return [convertToFloat(s) for s in value]
     else:
         return convertToFloat(value)
     
 def convertToFloat(value):
-    __suffix = {'y': 'e-24',  # yocto
-                'z': 'e-21',  # zepto
-                'a': 'e-18',  # atto
-                'f': 'e-15',  # femto
-                'p': 'e-12',  # pico
-                'n': 'e-9',   # nano
-                'u': 'e-6',   # micro
-                'm': 'e-3',   # mili
-                'c': 'e-2',   # centi
-                'd': 'e-1',   # deci
-                'k': 'e3',    # kilo
-                'M': 'e6',    # mega
-                'G': 'e9',    # giga
-                'T': 'e12',   # tera
-                'P': 'e15'   # peta
-                }
-    
-    value = str(value)
     
-    for i, j in __suffix.iteritems():
-        value=value.replace(i, str(j))
+    try:
+        # first just try and convert the value
+        return float(value)
+        
+    except ValueError as ex:
+        # Catch any casting exeception
+        value = value.strip()
+        
+        # only the last value can be an SI scaling letter 
+        last = value[-1]
+
+        if last in __suffix:
+            # remove last character and append the SI scaling
+            value = value[0:-1] + __suffix[last]
+        else:
+            raise pkex.BasePyKatException("Could not convert SI scaling in '{0}' to a float".format(value))
         
-    return float(value)
+        try:   
+            return float(value)
+        except ValueError as ex:
+            raise pkex.BasePyKatException("Unable to convert '{0}' into a float".format(value))