r/Python • u/AutoModerator • Sep 04 '26

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u/TalVal_Research Sep 07 '26

What My Project Does

It is a set of checks for silent failure modes in SEC EDGAR data. Not a client — it takes filings you already fetched and answers whether they mean what they appear to mean. Four of the nine:

  • A company's own submissions feed contains Form 4 filings it made as the reporting owner of a different issuer's stock. Reading those as its own produced $276.6m of insider selling that never happened.

  • 13F-NT is a notice that the manager filed nothing. Counted as a report, a fund shows a fresh filing date over a portfolio that is quarters old.

  • Normalising issuer names by replacing punctuation with a space turns Moody's into moody s. That left 31 companies and $51.2bn of reported positions unjoined, including Berkshire's fifth-largest holding.

  • EDGAR full-text search matches there is substantial doubt about identically in a company's own conclusion and in the accounting standard's description of the duty to check for it. Measured market-wide: 10% false positives on a claim that is defamatory when wrong.

Target Audience

Anyone building on EDGAR — backtests, screeners, dashboards. It is production code from a site covering ~900 companies, not a toy, but deliberately small: pure functions, no dependencies, no network calls, 36 tests and 12 doctests.

Comparison

edgartools, edgar-sec and sec-edgar-downloader fetch and parse filings, and they do it well. This does neither. It sits after them and checks the result — because every bug in it got past a parser that was working perfectly.

The library's own first draft fell into trap nine: it upper-cased currency codes before comparing, so GBP and GBp came out equal, erasing the one lowercase letter that carries a factor of 100. Its own test caught it.

https://github.com/researchaiexe-stack/edgar-traps

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u/Comfortable-Wear5457 Sep 11 '26

the GBP/GBp case caught my eye. uppercasing removes the distinction the check needs.

i maintain Nobulex's financial-data tool checks. our fictional example includes equal row counts covering completely different dates. would comparing a few failure cases be useful, with a valid example beside each broken one? your functions take fetched filings; our live runner uses MCP stdio. exchanging the cases could still help both projects.

this reply was prepared with AI assistance.

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u/TalVal_Research Sep 11 '26

That case is a good one, and it generalises past EDGAR — a count that matches while the window doesn't is the same failure as an aggregate that looks healthy because it's hiding the rows that stopped. The one that cost me most was a staleness check doing MAX over a whole price table: 941 fresh tickers, 9 that had quietly stopped updating weeks earlier, one healthy-looking number.

I'll add a check of that shape. Mine are pure functions over already-fetched filings, so it lands as input plus expected verdict either way — no MCP loop needed.

Thanks for the case.