gomarc: MARC21 for Go, 4x–11x faster than pymarc

If you work with library data, you work with MARC21 — the length-prefixed binary record format catalogues have run on since the 1960s, complete with a directory of field offsets, subfield delimiters, and a pre-Unicode character encoding called MARC-8 that needs a lookup table with thousands of entries to decode. In Python that problem is solved: pymarc is mature, complete, and pleasant to use. In Go it wasn't. gomarc is a port of pymarc to Go. It covers the binary MARC21 transmission format, MARC-8 to Unicode conversion, MARCXML, and MARC-in-JSON — and on real catalogue exports it runs 4x to 11x faster than the library it was ported from. go get github.com/beyto1974/gomarc@v0.1.0 It reads like pymarc If you know pymarc, you already know this API. Iterate records, pull the fields you want: reader := marc . NewReader ( f ) for { record , err := reader . Next () if errors . Is ( err , io . EOF ) { break } if err != nil { log . Println ( err ) // permissive: bad records are skipped, not fatal continue } title , _ := record . Title () fmt . Println ( title ) } Title , Author , ISBN , ISSN , Subjects , Publisher , PubYear and more are there as methods. For anything else, go at the tag and subfield directly: value , ok := record . Get ( "245" ) . Subfield ( "a" ) for _ , f := range record . GetFields ( "650" ) { fmt . Println ( f ) } Build records, modify them, write them back: record . Get ( "245" ) . SetSubfield ( "a" , "The Zombie Programmer : " ) writer := marc . NewWriter ( out ) writer . Write ( record ) And convert to the formats the rest of your stack can actually read — both use UTF-8 throughout instead of MARC-8, so standard tooling works: s , err := record . AsJSON () // MARC-in-JSON records , err := marc . ParseXML ( r ) // MARCXML Large MARCXML files stream one record at a time via marc.NewXMLReader rather than loading into memory. The numbers Two real catalogue exports — 138,076 records, 166 MB. AMD Ryzen 5 3600, Go 1.25.12, CPython 3.13.5, gomarc v0.1.0, pym