FWIW, in vanilla emacs, I cannot find python-execute-file, but looks like it is similar to python-shell-send-file in stock emacs.
python-shell-send-file (bound by default to C-c C-l) prompts the user to select the file they want to send to the python-shell-interpreter (default value is "python").. it need not be the current file or one of the open Python files.
python-shell-send-buffer (bound by default to C-c C-c) sends the current buffer to the python-shell-interpreter without asking any questions.
So if you want to quickly want to evaluate the script you are currently working on, you would use python-shell-send-buffer. But if you want to evaluation some other file (already open or not), you would use python-shell-send-file (or may be python-execute-file).
python-execute-filefunction in python mode, but Spacemacs seems to have a function with a similar name:spacemacs/python-execute-file.