Forms

This was a one-off, quick-and-dirty Python project I wrote during a week at a summer internship. The company had a few dozen items it had received from the U.S. Navy over a decade prior which it was getting rid of, and for which there was no documentation for the original issue. Because the equipment had been issued by the Navy, it had to be returned to the Navy, which meant a whole lot of paperwork.

My time in the Army made me intimately familiar with military equipment turn-in procedures, so I knew that this can be a tedious process with just a handful of items. The thought of generating all these forms "by hand" in quadruplicate was just too tedious to bear, and introduced too many chances for transcription errors.

Python to the rescue!

The script fdftest.py solved this problem. It accepts CSV input, mapping the columns to the fields in DoD Form 1348-1A which were required by the DLA¹ Disposition Services Office we were turning this equipment into, and produces filled-in copies of the form complete with scannable barcodes.

Things I learned

This was a custom-tailored script designed to do a single specific task, and would take more effort than I feel it's worth to generalize into a broader solution. It would require accounting for so many unknowns as to be impractical.

However, this was a very rewarding project because it solved a problem with 100% accuracy that I knew from firsthand experience to be a PITA².

Barcodes

Using a simple smartphone barcode scanner app, I determined the style of barcode used on the sample form sent to us by the DLA office. As it turns out, many barcodes can be reproduced in PDFs by simply setting the field font to one of the many standard barcode fonts. All that's required after that is to supply the plaintext corresponding to the decoded barcode, and the PDF software will render the barcode properly.

PDF/FDF file structure

I learned about the internal structure of a PDF file. PDFs are largely binary data, but there is an intermediate format called Forms Data Format (FDF) which stores the content of the forms in plaintext. The general form is << /T (key) /V (value) >>.

Once I learned how the file internals needed to be organized, writing the script was very straightforward. The conversion to PDF was accomplished via a system call to the PDFtk tookit.

Document number format

Each item turned in required its own form, and each form required a unique ID number in a specific format, called a Document Number, which is the concatenation of the following items:

• DODAAC: Department of Defense Activity Address Code. A six-digit alphanumeric code that identifies the unit to which the equipment belongs
• Julian date: a four-digit date of the form Yddd, where Y is the last digit of the current calendar year, and ddd is the day of the year on which the document was generated
• ID number: a four-digit arbitrary but unique positive integer. The only requirement is that no two documents can have the same ID number for a given Julian date. Cannot be 0000.

I wrote the following function to generate Document Numbers:

# "constants" for PDF form
fdf_static_content = {
    'DODAAC_FROM': 'N00060',
    ...
}

# DOCNO stuff
id = 1
def getDocNo():
    day_of_year = str(datetime.today().timetuple().tm_yday)
    julian_year = str(datetime.today().timetuple().tm_year)[3:]
    
    global id
    docNo = fdf_static_content['DODAAC_FROM'] + julian_year + day_of_year + f'{id:0>{4}}'
    id += 1
    return docNo

Flow

flowchart TD
    A[Excel Inventory Spreadsheet] -->|Modify Column Headers| B[Export to CSV]
    B --> C[Convert to FDF]
    C --> D[Use PDFtk to populate template]

Loading

Sketching the problem

# populate n PDFs with data from a CSV file, n = num records in CSV file
    # read CSV
    # for each record in CSV
        # generate temp FDF
            # field mapping (see below)
        # populate PDF with FDF data
            # (system|subprocess).run(pdftk...)

Footnotes

1. Defense Logistics Agency ↩

2. I'm sure you know what this means. ↩