CUSIP Regex for Python

What this pattern does

This page provides a lightweight, single-purpose regular expression for matching cusip, ported and verified for Python. Financial data validation has zero tolerance for false negatives — a missed invalid entry can corrupt downstream calculations. The snippet below is ready to drop into your Python project — whether you're validating in a Django view, a FastAPI endpoint, or a standalone data processing script.

Python Implementation

# CUSIP
# ReDoS-safe | RegexVault — Finance > Securities & Trading

import re

cusip_pattern = re.compile(r'^[0-9A-Z]{5}[0-9A-Z]{3}[0-9]$')

def validate_cusip(value: str) -> bool:
    return bool(cusip_pattern.fullmatch(value))

# Example
print(validate_cusip("037833100"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Securities & Trading category and carries a ReDoS-safe certification. That matters for Python developers because particularly important in Python web servers where CPU-bound regex operations can stall concurrent request handling. RegexVault audits patterns against known backtracking attack vectors, ensuring you have the necessary context before using this regex in a high-stakes production environment.

Common Pitfalls

Technical Notes

Structure: 6-char issuer code + 2-char issue number + 1 check digit. The issuer code identifies the company; the issue number identifies the specific security class. Check digit uses a weighted Luhn-like algorithm.