More tricky fib-exec example

Author: rocky

test/example/fib-exec.py

@@ -3,5 +3,6 @@ def fib(x: int) -> int:
         return 1
     return fib(x-1) + fib(x-2)
 
-exec("print(fib(2))")
+command = "print(fib(2))"
+exec(command)
 print("fib(2)= %d, fib(3) = %d, fib(4) = %d\n" % (fib(2), fib(3), fib(4)))