Extract PDF pages from a single PDF file with range

pdf_extract.py

from argparse import ArgumentParser
from PyPDF2 import PdfFileReader, PdfWriter


def main():
    parser = ArgumentParser(
        prog="A simple PDF page extractor",
        description="A simple PDF page extractor",
        epilog="Text at the bottom for help"
    )
    parser.add_argument("input")
    parser.add_argument("output")
    parser.add_argument("start")
    parser.add_argument("to")

    args = parser.parse_args()

    input_file = args.input
    output_file = args.output
    start = int(args.start)
    to = int(args.to)

    if start < 0 or to < 0:
        raise "Starting and ending page must be a natural number."

    if start > to:
        raise "Starting page must be smaller than ending page."

    with open(input_file, 'rb') as reader:
        pdf = PdfFileReader(reader)
        info = pdf.getDocumentInfo()
        page_num = pdf.getNumPages()

        if start > page_num or to > page_num:
            raise f"Either the starting page or ending page is out of range of the file pages. " \
                  f"The file has {page_num} pages."

        pdf_out = PdfWriter()
        for i in range(start, to):
            pdf_out.addPage(pdf.getPage(i))
        pdf_out.write(output_file)

        print("Extraction finished.")


if __name__ == '__main__':
    main()