Avg:不能使用非数字字符串作为操作数和“+”

This a code to simulate an MM1 queue server (not really an important fact). I'm trying to get the average value to the number of packets in the queue for each run. Given that I read the value of lambda from a file, modify it, save the new modified value of it in the file again, and run the simulation with current value of lambda:This a code to simulate an MM1 queue server (no