function to generate pdf chunks

[spfeifer222]

I tried to write a function to create pdf_chunk files via pdftk syntax:

pdftk in.pdf cat 1-end output out.pdf

using:

def gen_pdfchunks(pdf_path, chunksize=5, first=1, last='end'):
    '''
    Generate chunks of large pdf files.
    '''
    cleanOnFail = True
    out_dir = tempfile.mkdtemp()
    chunk_file = '%s/chunk.pdf' % out_dir

    page = first
    if last == 'end':
        last_page = pypdftk.get_num_pages(pdf_path)
    else:
        last_page = int(last)

    # pdftk: pdftk in.pdf cat 1-5 output out1.pdf
    while page <= last_page:
        args = [PDFTK_PATH, pdf_path, 'cat']
        if page + chunksize - 1 > last_page:
            args += str(page)+'-'+str(last_page)
        else:
            args += str(page)+'-'+str(chunksize-1)
        args += ['output', chunk_file]
        try:
            run_command(args)
        except:
            if cleanOnFail:
                shutil.rmtree(out_dir)
            raise
        page += chunksize
        yield chunk_file

Calling

chunk_gen = gen_pdfchunks(file)
next(chunk_gen)

with a valid pdf file in varibale file the folling output is produced:

Error: Unexpected range end; expected a page
   number or legal keyword, here: 
   Exiting.
Errors encountered.  No output created.
Done.  Input errors, so no output created.
---------------------------------------------------------------------------
CalledProcessError                        Traceback (most recent call last)
<ipython-input-71-8f19f4570272> in <module>
----> 1 next(chunk_gen)

<ipython-input-69-9da5f665d933> in gen_pdfchunks(pdf_path, chunksize, first, last)
     22         args += ['output', chunk_file]
     23         try:
---> 24             run_command(args)
     25         except:
     26             if cleanOnFail:

<ipython-input-38-64212d8798aa> in run_command(command, shell)
     14 def run_command(command, shell=False):
     15     ''' run a system command and yield output '''
---> 16     p = check_output(command, shell=shell)
     17     return p.split(b'\n')
     18 

<ipython-input-38-64212d8798aa> in check_output(*popenargs, **kwargs)
      9         if cmd is None:
     10             cmd = popenargs[0]
---> 11         raise subprocess.CalledProcessError(retcode, cmd, output=output)
     12     return output
     13 

CalledProcessError: Command '['/usr/bin/pdftk', '/home/pfeifer/Multimedia/Bücher@LP/Akupunktur/Praxis Akupressur - Christina Mildt.pdf', 'cat', '1', '-', '4', 'output', '/tmp/tmp32l4j3vt/chunk.pdf']' returned non-zero exit status 1.

The problem is, that the given page range for the chunks does not keep one string, e.g. with chunksize=5 this should be 1-4 instead of 1 - 4 which is what the command in the CalledProcessError line is doing.

I just started to write in Python, but like to contribute to the project. I am not 100% confident that the code would do what I want, if the error not have been raised. In order to improve the project and my skills I like to ask for suggestions to clean/improve/correct my given code and of course help in developing the desired function.

Best regards,
Sebastian

[revolunet]

Hi Sebastian, thanks for reporting

The thing is this line args+=str(page)+'-'+str(chunksize-1) doesnt append one item to args but three items separately

you could use args.append(str(page)+'-'+str(chunksize-1)) instead