Cron Expression (Standard 5-Field) Regex for Python

What this pattern does

This page provides a comprehensive, battle-tested regular expression for matching cron expression (standard 5-field), 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

# Cron Expression (Standard 5-Field)
# ReDoS-safe | RegexVault — Dev & Systems > Cron

import re

cron_expression_standard_5field_pattern = re.compile(r'^(\*|[0-9]|[1-5][0-9])(?:[-/,](?:[0-9]|[1-5][0-9]))? (\*|[01]?[0-9]|2[0-3])(?:[-/,](?:[01]?[0-9]|2[0-3]))? (\*|[1-9]|[12][0-9]|3[01])(?:[-/,](?:[1-9]|[12][0-9]|3[01]))? (\*|[1-9]|1[0-2])(?:[-/,](?:[1-9]|1[0-2]))? (\*|[0-7])(?:[-/,][0-7])?$')

def validate_cron_expression_standard_5field(value: str) -> bool:
    return bool(cron_expression_standard_5field_pattern.fullmatch(value))

# Example
print(validate_cron_expression_standard_5field("* * * * *"))  # True

Test Cases

When to use this pattern

This pattern is drawn from the Dev & Systems > Cron 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

5 space-separated fields: minute (0-59), hour (0-23), day-of-month (1-31), month (1-12), day-of-week (0-7). Both 0 and 7 are Sunday. Does not catch logically impossible date combinations. Use a dedicated cron library for full semantic validation.