wcwidth

wcwidth is a simple, focused library that does exactly one thing: calculates the display width of Unicode strings in terminals. It's pure Python with zero dependencies, which makes it trivial to integrate without worrying about transitive dependency hell. The API is dead simple - wcwidth() for single characters and wcswidth() for strings - and it handles edge cases like zero-width joiners, combining characters, and wide CJK characters correctly.

From an operations perspective, this library is a dream. Memory footprint is negligible, performance is excellent for typical use cases (sub-microsecond for most strings), and there's literally nothing to configure or tune. No connection pools, no retries, no timeouts - it's just a pure function that does math. The Unicode table data is embedded, so no file I/O or network calls to worry about.

The main limitation is that it's synchronous-only and you can't lazy-load the Unicode tables, so every process pays the ~100KB memory cost upfront. For high-scale deployments with thousands of workers, this adds up, though it's still minor. Breaking changes between 0.1.x and 0.2.x around East Asian Width handling caught some users, but the API has been stable since.

wcwidth does exactly one thing: calculates the display width of Unicode strings in terminals. From a security standpoint, this is refreshingly simple—pure Python implementation with zero dependencies means no supply chain risk. The library handles edge cases well, returning -1 for non-printable characters rather than throwing exceptions, which prevents information leakage through error messages.

The main security consideration is that it bundles Unicode width tables that can lag behind current standards. This isn't a vulnerability per se, but could lead to display width miscalculations with newer emoji or Unicode additions. Input validation is implicit—the library accepts any string and handles malformed input gracefully without crashes. No network calls, no file I/O, no crypto—just deterministic character width lookups.

In practice, it's dead simple: call wcwidth() for single characters or wcswidth() for strings. The API is intentionally minimal, which I appreciate from a security perspective. The library doesn't expose stack traces or internal state on bad input, just returns sensible defaults.

In production, wcwidth is essentially invisible—which is exactly what you want from a utility library. It's a pure function that takes a character or string and returns the display width. No configuration, no connection pools, no state. Memory footprint is negligible since it's just lookup tables for Unicode data. Performance is excellent for typical terminal rendering workloads; I've used it in hot loops formatting thousands of lines without issues.

The error handling is straightforward: invalid input returns -1 or raises standard Python exceptions. No custom exceptions to catch, no retry logic needed. It's deterministic and side-effect free, making it trivial to test and reason about. The main gotcha is remembering that wcwidth() returns width for a single character while wcswidth() handles strings—the naming trips people up initially.

From an operations perspective, this is a "set it and forget it" dependency. No logs to configure, no timeouts to tune, no resource cleanup. Version updates have been non-breaking in my experience. The Unicode version it implements may lag slightly behind the latest spec, but this rarely matters in practice for terminal applications.