Hy is a dialect of the Lisp programming language designed to interact with Python by translating s-expressions into Python's abstract syntax tree (AST).[2][3] Hy was introduced at Python Conference (PyCon) 2013 by Paul Tagliamonte.[4] Lisp allows operating on code as data (metaprogramming), thus Hy can be used to write domain-specific languages.[5]
Similar to Kawa's and Clojure's mappings onto the Java virtual machine (JVM),[6][7] Hy is meant to operate as a transparent Lisp front-end for Python.[8] It allows Python libraries, including the standard library, to be imported and accessed alongside Hy code with a compiling[note 1] step where both languages are converted into Python's AST.[note 2][9][10][11]
From the language documentation:[12]
=> (print "Hy!") Hy! => (defn salutationsnm [name] (print (+ "Hy " name "!"))) => (salutationsnm "YourName") Hy YourName!