You load a credit card transaction CSV into pandas. The amount column looks numeric, for example three transactions of 1,250.00, 80.50 and 300, but when you sum it you get one long concatenated string, or sometimes an error. What is going on, and how would you fix it?

你用pandas读了一份信用卡交易CSV，金额那列看着像数字，比如1,250.00、80.50、300这三笔，可你一求和，出来的是一长串拼在一起的字符，有时候还直接报错。这是怎么回事？你会怎么处理？