isodate

isodate is a straightforward library for parsing and formatting ISO 8601 datetime strings. From a security perspective, it handles malformed input gracefully with well-defined exceptions (ISO8601Error) that don't leak sensitive information. The parser is strict by default, which aligns with secure-by-default principles - it won't silently accept ambiguous or invalid date strings that could lead to logic bugs.

The library has zero dependencies beyond Python's standard library, which significantly reduces supply chain risk. This is a major win for security-conscious teams. CVE history is clean, and the codebase is small enough to audit if needed. Error messages are descriptive without exposing internals, making it safe for use in API validation layers.

One caveat: you need to handle timezone-aware vs naive datetime objects carefully, as the library returns what the input specifies. This can lead to comparison errors if you're not explicit about timezone handling in your application logic. The duration parsing is particularly useful for API inputs, but requires validation of the resulting timedelta objects to prevent resource exhaustion attacks with extremely large durations.

In production systems handling API responses and data serialization, isodate does exactly what it promises with minimal fuss. The library is lightweight, has zero dependencies beyond the standard library, and the parsing performance is consistently fast even under high load. Memory footprint is negligible since it's purely functional transformations to native Python datetime objects. The API is straightforward: parse_datetime(), parse_duration(), and their counterparts for formatting.

The error handling is predictable with ISO8601Error exceptions that include enough context for logging and debugging. However, duration parsing has some quirks - the library returns custom Duration objects rather than timedelta for complex durations (years/months), which can surprise you when doing arithmetic operations. You'll need to handle both types in your code or normalize immediately.

In terms of operations concerns, there's nothing to configure or tune - it's stateless with no connection pooling or resource management needed. This simplicity is actually a strength for high-throughput services. The library hasn't had breaking changes in years, making upgrades safe. Just be aware that timezone-naive strings default to naive datetime objects, so you need explicit handling for UTC assumptions.

The isodate library does exactly what it promises: parsing and formatting ISO 8601 dates, times, and durations. The API is straightforward with functions like `parse_datetime()`, `parse_date()`, and `parse_duration()` that just work. You import what you need and pass strings in - no configuration wrestling required. The duration parsing is particularly useful since Python's standard library doesn't handle ISO 8601 durations natively.

The main friction point is the complete absence of type hints, which feels dated in 2024. You'll need to check documentation or source code to understand what types are returned. Error messages when parsing fails are adequate but not great - you get ISO8601Error exceptions that tell you parsing failed but don't always clearly explain why your input was invalid.

Documentation exists but is minimal. The README covers basic usage patterns which is usually enough, but edge cases require digging into the code. Despite these shortcomings, it's battle-tested and reliable for the core use case of parsing ISO 8601 strings into Python datetime objects.