Environment Variable Secret Pattern (.env file) Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching environment variable secret pattern (.env file), ported and verified for Python. In security-sensitive code, using an unverified regex can open the door to both false positives and denial-of-service attacks. 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

# Environment Variable Secret Pattern (.env file)
# ReDoS-safe | RegexVault — Security > Secrets & Config

import re

environment_variable_secret_pattern_env_file_pattern = re.compile(r'^((?:[A-Z_]+)?(?:PASSWORD|SECRET|TOKEN|KEY|CREDENTIAL|AUTH|API)[A-Z_]*)=([^\r\n#]{8,})$')

def validate_environment_variable_secret_pattern_env_file(value: str) -> bool:
    return bool(environment_variable_secret_pattern_env_file_pattern.fullmatch(value))

# Example
print(validate_environment_variable_secret_pattern_env_file("DATABASE_PASSWORD=mySecretPassword123"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Security > Secrets & Config 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

.env files should never be committed to version control. Use .gitignore to exclude .env files. The pattern uses multiline mode to match line-by-line. Capture group 1=key name, group 2=value. Value must be at least 8 chars to reduce false positives.