Validate container numbers from shipping documents.

01 / INSTALL AND GET A KEY

One dependency. Your first 100 pages are free, no card, at pennyocr.com/dashboard.

pip install pennyocr
export PENNYOCR_API_KEY=pk_live_...

02 / READ THE DOCUMENT

from pennyocr import PennyOCR

result = PennyOCR().ocr("bill-of-lading.pdf", format="text")
text = result.text

03 / WHAT YOU GET BACK

The page in reading order. Container numbers appear with or without spaces and hyphens:

**BILL OF LADING**  B/L No: MAEU240117653
Container / Seal: CSQU 305438 3 / SL-88213, MSKU-1234565

04 / FIND THE CONTAINER NUMBERS

Four letters (owner code plus U, J or Z), six digits and a check digit, with optional separators:

import re

CONTAINER_RE = re.compile(r"\b([A-Z]{3}[UJZ])[\s-]?(\d{6})[\s-]?(\d)\b")
found = ["".join(m) for m in CONTAINER_RE.findall(text)]
print(found)

05 / VALIDATE THE CHECK DIGIT

Each character gets a value (letters skip multiples of 11), weighted by powers of 2. The sum mod 11, mod 10, must equal the last digit.

# ISO 6346 letter values skip multiples of 11 (11, 22, 33).
LETTERS = {c: v for c, v in zip("ABCDEFGHIJKLMNOPQRSTUVWXYZ",
           [n for n in range(10, 39) if n % 11])}

def container_is_valid(number: str) -> bool:
    """The 11th character is a check digit over the first 10."""
    total = sum((LETTERS[c] if c.isalpha() else int(c)) * 2 ** i
                for i, c in enumerate(number[:10]))
    return total % 11 % 10 == int(number[10])

for n in found:
    print(n, "ok" if container_is_valid(n) else "CHECK FAILED - send for review")