It&#x27;s likely that the big overhead slowdowns come from points where an object containing many typed elements is passed through without processing. This requires field by field checking, in the form of dynamic checks in a naive implementation.  This could be repeated through several levels of function calls before the object is used.  Mixing typed and untyped code makes this very likely.<p>It&#x27;s a big concern that Python is going this route.  With terrible syntax, too. Some type info is in comments, because it couldn&#x27;t be crammed  into the syntax, but some type info is in non-comment &quot;annotations&quot;.  I&#x27;ve been saying for a while, &quot;Stop Python&#x27;s little tin god before he kills again&quot;. Python 4 may be headed for another Python 3 like debacle.