Environment Variable Assignment (KEY=value) Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching environment variable assignment (key=value), ported and verified for Python. A rigorously tested regex reduces debugging time and protects your application from edge-case failures. 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 Assignment (KEY=value)
# ReDoS-safe | RegexVault — Dev & Systems > Environment

import re

environment_variable_assignment_keyvalue_pattern = re.compile(r'^([A-Za-z_][A-Za-z0-9_]{0,254})=(.*)$')

def validate_environment_variable_assignment_keyvalue(value: str) -> bool:
    return bool(environment_variable_assignment_keyvalue_pattern.fullmatch(value))

# Example
print(validate_environment_variable_assignment_keyvalue("NODE_ENV=production"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Environment 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

Group 1 = variable name, group 2 = value (may be empty). An empty value (VAR=) means the variable exists with an empty value, distinct from an unset variable.