Getting ready for physics class

I was able to complete the project with fairly little issue outside fo me just not reading the question properly, but i do have a question regarding printing my outputs. Going through the video after the fact just to see if there was anything i did wrong or could have done better i saw him use str(train_work) as an example. I was able to print the exact same without doing that because i deperated with , instead of +. Is there any specific reason to use his method, or does it generally come down to preference?

I’m not an expert, but I’m pretty sure that is all about the readability of the code, so there is no other reason beside that