Code modernization.  Replace v=s[i]; del s[i] with single lookup v=s.pop(i)
diff --git a/Lib/multifile.py b/Lib/multifile.py
index ff7dbf6..4ef3644 100644
--- a/Lib/multifile.py
+++ b/Lib/multifile.py
@@ -160,8 +160,7 @@
         self.level = max(0, self.level - 1)
         del self.stack[0]
         if self.seekable:
-            self.start = self.posstack[0]
-            del self.posstack[0]
+            self.start = self.posstack.pop(0)
             if self.level > 0:
                 self.lastpos = abslastpos - self.start