====== Use Page Ranges in PyPDF2 PdfFileMerger ======

[[https://pythonhosted.org/PyPDF2/PdfFileMerger.html|PdfFileMerger]] is a nice Python class provided by the PyPDF package.
If you want to catenate multiple pages using expressions you can use a [[https://pythonhosted.org/PyPDF2/Easy%20Concatenation%20Script.html#page-range|Page Range expression]].

To specify page ranges, you need to import the PageRange class
  from PyPDF2 import PdfFileMerger, PageRange

then you can specify the range as a PageRange() object. For example, the range from page 13 (**REMEMBER: page indices start with zero.!**) to the last one can be written:
  merger.append(inpdf, pages=PageRange('13:-1'))

More page range expression examples follows, if you want to play a bit with them:
    :     all pages.                   -1    last page.
    22    just the 23rd page.          :-1   all but the last page.
    0:3   the first three pages.       -2    second-to-last page.
    :3    the first three pages.       -2:   last two pages.
    5:    from the sixth page onward.  -3:-1 third & second to last.

The third, "stride" or "step" number is also recognized.
    ::2       0 2 4 ... to the end.    3:0:-1    3 2 1 but not 0.
    1:10:2    1 3 5 7 9                2::-1     2 1 0.
    ::-1      all pages in reverse order.

See below for a complete working python script with PyPDF2 and page ranges. Just set the in/out filenames, the starting/ending page numbers and run the script:

  from PyPDF2 import PdfFileMerger, PdfFileReader, PageRange
  
  infn = "infilename.pdf"
  outfn = "outfilename.pdf"
  startpage = 5 #set starting page in the pdf -1 (i.e. here we want to start from page 6)
  endpage = -1  #last page
  
  srcfile = PdfFileReader(infn, 'rb')
  merger = PdfFileMerger()
  page_range = str(startpage) + ':' + str(endpage)
  merger.append(srcfile, pages=PageRange(page_range))
  merger.write(outfn)

And if you are using Ubuntu, remember to install pypdf2 package first
  sudo apt install python3-pypdf2