allow max_seq_length=0 to disable truncation altogether

IPython/lib/pretty.py

@@ -330,7 +330,7 b' class PrettyPrinter(_PrettyPrinterBase):'
     def _enumerate(self, seq):
         """like enumerate, but with an upper limit on the number of items"""
         for idx, x in enumerate(seq):
-            if idx >= self.max_seq_length:
+            if self.max_seq_length and idx >= self.max_seq_length:
                 self.text(',')
                 self.breakable()
                 self.text('...')