Market Identifier Code (MIC) Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching market identifier code (mic), 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

# Market Identifier Code (MIC)
# ReDoS-safe | RegexVault — Finance > Securities & Trading

import re

market_identifier_code_mic_pattern = re.compile(r'^(?!NYSE$)[A-Z0-9]{4}$')

def validate_market_identifier_code_mic(value: str) -> bool:
    return bool(market_identifier_code_mic_pattern.fullmatch(value))

# Example
print(validate_market_identifier_code_mic("XNYS"))  # 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

ISO 10383 MICs: XNYS=NYSE, XNAS=NASDAQ, XLON=LSE, XTKS=TSE Tokyo, XHKG=Hong Kong, XSES=SGX Singapore. The X prefix denotes the primary/regulated market. S prefix for segments.