Lot Size / Quantity (Financial) Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching lot size / quantity (financial), 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

# Lot Size / Quantity (Financial)
# ReDoS-safe | RegexVault — Finance > Financial Formats

import re

lot_size_quantity_financial_pattern = re.compile(r'^(?:(?!0[0-9])[0-9]+(?:\.[0-9]*[1-9])?|0\.[0-9]*[1-9])$')

def validate_lot_size_quantity_financial(value: str) -> bool:
    return bool(lot_size_quantity_financial_pattern.fullmatch(value))

# Example
print(validate_lot_size_quantity_financial("100"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Finance > Financial Formats 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

Covers everything from stock lots (integer) to fractional crypto amounts (8 decimal places for Bitcoin). Rejects scientific notation (1e5) — always expand to decimal form for financial quantities.