A value is trying to be set on a copy of a slice from a DataFrame.

读取完csv文件，进行运算，重新复制弹出A value is trying to be set on a copy of a slice from a DataFrame.

解决方法如下：

个人理解是这里的变量引用是直接寻址，不允许改变原变量的值，要将原变量的值复制出来，进行运算。个人理解，有错误还请指出学习一下