Not running on Ubuntu18

[xmarti6]

Waw thanks a lot! it saved me a lot of time. In my case, using a large PDF, did not work at first attempt:

I had this error output:

Error: /undefinedfilename in (page_1.pdf)
Operand stack:

Execution stack:
   %interp_exit   .runexec2   --nostringval--   --nostringval--   --nostringval--   2   %stopped_push   --nostringval--   --nostringval--   --nostringval--   false   1   %stopped_push
Dictionary stack:
   --dict:974/1684(ro)(G)--   --dict:0/20(G)--   --dict:77/200(L)--
Current allocation mode is local
Last OS error: No such file or directory
GPL Ghostscript 9.26: Unrecoverable error, exit code 1

However, I could make the code work by changing these lines:

for file in onlyfiles:
    if file.startswith('page_') :
        pg = file.split('_')[1]
        #print(pg, type(pg), int(pg[:2]) < 10, pg[:2]) #debug
        c = 'mv -f '+file+' page_'+pg.strip("0")
        #print(c) #debug
        subprocess.call(c, shell=True, cwd=temp_dir) #debug . commented

For the installation I ran the commands like this in Ubuntu:

sudo apt-get install python-pip
./pdftk_installer      #seee: https://askubuntu.com/questions/1028522/how-can-i-install-pdftk-in-ubuntu-18-04-and-later
sudo apt-get install ghostscript
pip install pypdftk
pip install natsort
#Calling the program: 
python main.py

Hope this helps others in a similar context.
Best