Jupyter Notebook and previous output
usually, yes, so long as the kernel is still up.  the return values of all expressions evaluated are stored in the Out global list.  If you are now executing statement number n, then Out[n-1] will have the last thing you successfully finished.
if your output was not returned, but rather printed. You're out of luck...
Is there any way to see the previous output without rerunning the program? For example, I left my ML algorithm to work overnight and in the morning I got the results. But, for some reason, when I pressed Enter on the original code, it started to run again and the original output disappeared.