Windows Absolute Path (Drive Letter) Regex for Python

What this pattern does

This page provides a well-structured, multi-part regular expression for matching windows absolute path (drive letter), 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

# Windows Absolute Path (Drive Letter)
# ReDoS-safe | RegexVault — Dev & Systems > File Paths

import re

windows_absolute_path_drive_letter_pattern = re.compile(r'^[a-zA-Z]:(?:\\{1,2}|\/)(?:[^\\/:*?"<>|\r\n]+(?:\\{1,2}|\/))*[^\\/:*?"<>|\r\n]*$')

def validate_windows_absolute_path_drive_letter(value: str) -> bool:
    return bool(windows_absolute_path_drive_letter_pattern.fullmatch(value))

# Example
print(validate_windows_absolute_path_drive_letter("C:\\Users\\user\\Documents"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > File Paths 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

Windows reserved characters < > : " | ? * are excluded. The pattern accepts both backslash and forward slash. Drive letters are A-Z. UNC paths (\\\\server\\share) require dev-path-06.