TypeError: 'NoneType' object is not iterable

[Don-Yin]

There appears to be a type error in "finder.py" that only emerges on certain PDF files. This one, for example:
paper12.2009_unknown_040916_440842.pdf

A miniumn code snippet for reproducing this error:

from pathlib import Path
import pdf2doi

pdf2doi.config.set("verbose", False)
PDF_name = "paper12.2009_unknown_040916_440842.pdf"
results = pdf2doi.pdf2doi(str(Path("examples", PDF_name)))

Where the PDF is placed in the example folder.

Here is the error message:

Traceback (most recent call last):
  File "/Users/donyin/Desktop/pdf2doi-master/main.py", line 15, in <module>
    results = pdf2doi.pdf2doi(str(Path("examples", i)))
  File "/Users/donyin/Desktop/pdf2doi-master/pdf2doi/main.py", line 90, in pdf2doi
    result = pdf2doi_singlefile(filename)
  File "/Users/donyin/Desktop/pdf2doi-master/pdf2doi/main.py", line 134, in pdf2doi_singlefile
    result = finders.find_identifier(file,method="document_infos",keysToCheckFirst=['/doi','/identfier'])
  File "/Users/donyin/Desktop/pdf2doi-master/pdf2doi/finders.py", line 548, in find_identifier
    identifier, desc, info = finder_methods[method](file,func_validate,**kwargs)
  File "/Users/donyin/Desktop/pdf2doi-master/pdf2doi/finders.py", line 586, in find_identifier_in_pdf_info
    identifier,desc,info = find_identifier_in_text(pdfinfo[key],func_validate)
  File "/Users/donyin/Desktop/pdf2doi-master/pdf2doi/finders.py", line 286, in find_identifier_in_text
    for identifier in identifiers:
TypeError: 'NoneType' object is not iterable

I thought I fixed this error by adding:

if identifiers is None:
     identifiers = []

at line 286 of your "finder.py", so that it becomes:

        #First we look for DOI
        for v in range(len(doi_regexp)):
            identifiers = extract_doi_from_text(text,version=v)
            if identifiers is None: # <- here
                identifiers = [] # <- here
            for identifier in identifiers:
                validation = func_validate(identifier,'doi')
                if validation: 
                    return identifier, 'DOI', validation

But this was a bit hacky and not the proper solution. You'd undoubtedly know more about what's going on, so I thought I'd let you know about this.

And by the way, there are some deprecated syntax that you might want to address:

UserWarning: Page.extractText is deprecated and will be removed in PyPDF2 2.0.0. Use Page.extract_text instead. [_page.py:1003]
UserWarning: addMetadata is deprecated and will be removed in PyPDF2 2.0.0. Use add_metadata instead. [_writer.py:793]
UserWarning: Page.extractText is deprecated and will be removed in PyPDF2 2.0.0. Use Page.extract_text instead. [_page.py:1003]

cheers,
Don

[MicheleCotrufo]

Thanks a lot for reporting this! Indeed, it is due to the bug that you pointed out. I am quite puzzled why this bug has "manifested" only now, I would have excepted this situation to occur more often. Maybe I accidentally created it in the last version....

I fixed the bug by making sure that the functions extract_doi_from_text and extract_arxivID_from_text return an empty list instead of None when nothing is found. I also fixed the deprecates sintaxes that you pointed out. Thanks again!

I released the version 1.2rc1 on pypi, would you mind testing it on this pdf file again?

pip install pdf2doi==1.2rc1

[Don-Yin]

Thank you for responding! It is now operational! Well done!
Thank you for this fantastic project.

[alexmaehon]

same problem

[MicheleCotrufo]

same problem

alexmaehon, do you still get this error after upgrading to version 1.2rc1? If yes, can you send me the PDF file and the full traceback?

[MicheleCotrufo]

Thank you for responding! It is now operational! Well done! Thank you for this fantastic project.

Excellent, thanks for your help! I will release the 1.2 version later today, then.

[MicheleCotrufo]

This bug was fixed with version 1.2