Obvious simplification, now that "long" has disappeared.
diff --git a/Lib/csv.py b/Lib/csv.py
index 53ed90c..09f4cf4 100644
--- a/Lib/csv.py
+++ b/Lib/csv.py
@@ -369,7 +369,7 @@
 
             for col in list(columnTypes.keys()):
 
-                for thisType in [int, int, float, complex]:
+                for thisType in [int, float, complex]:
                     try:
                         thisType(row[col])
                         break
@@ -379,10 +379,6 @@
                     # fallback to length of string
                     thisType = len(row[col])
 
-                # treat longs as ints
-                if thisType == int:
-                    thisType = int
-
                 if thisType != columnTypes[col]:
                     if columnTypes[col] is None: # add new column type
                         columnTypes[col] = thisType