Colab finishes with a ^C
"^C" appears for multiple types of interrupt in Colab I noticed. Even if you just press on the stop button (to interrupt execution of a cell) it shows "^C". I can't think of any other reasons why it would show a "^C"
I met the same problem when I ran python in colab. I found that because the list I generated was too large, it should have occupied all the memory.