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Hy Cuddles.png
Cuddles the cuttlefish
Paradigm Multi-paradigm: procedural, functional, object-oriented, meta, reflective, generic
Family Lisp
Designed by Paul Tagliamonte
First appeared 2013
Preview release
0.14.0 - Feb 14, 2018
Scope lexical, optionally dynamic[citation needed]
OS Cross-platform
Filename extensions .hy
Website hylang.org

Hy (alternately, Hylang) is a dialect of the Lisp programming language designed to interact with Python by translating expressions into Python's abstract syntax tree (AST). Hy was introduced at PyCon 2013 by Paul Tagliamonte.[1]

Similar to Clojure's and Kawa's mapping of s-expressions onto the JVM,[2] Hy is meant to operate as a transparent Lisp front end to Python's abstract syntax.[3] Because Lisp allows operating on code as data, Hy can be used to write domain-specific languages.[4] Hy also allows Python libraries (including the standard library) to be imported and accessed alongside Hy code with a compilation[note 1] step converting the data structure of both into Python's AST.[note 2][5][6][7]

Example code[edit]

From the language documentation:[8]

=> (print "Hy!")
=> (defn salutationsnm [name] (print (+ "Hy " name "!")))
=> (salutationsnm "YourName")
Hy YourName!

See also[edit]


  1. ^ "Compiled" is a term which may apply to expressing Hy code in Python's AST or converting that AST into bytecode, the latter being dependent on the particular Python interpreter used and not Hy.
  2. ^ Hy is tested on Python 2.7, 3.4 through 3.6, and PyPy.


  1. ^ Paul Tagliamonte (2 April 2013). PyCon lightning talk (Speech). PyCon. Santa Clara. Retrieved 2 September 2014.
  2. ^ Turto, Tuukka (14 February 2014). "Programming Can Be Fun with Hy". Open Source For You. Retrieved 2 September 2014.
  3. ^ Edge, Jake (30 April 2014). "Getting Hy on Python". LWN.net. Retrieved 2 September 2014.
  4. ^ Paul Tagliamonte (11 April 2014). Getting Hy on Python: How to implement a Lisp front-end to Python (Speech). PyCon. Montreal. Retrieved 2 September 2014.
  5. ^ "Hy Documentation". hylang.org. Retrieved 3 September 2014.
  6. ^ Danjou, Julien (26 March 2014). "The AST". The Hacker's Guide to Python. pp. 165–172.
  7. ^ Kitchin, John (31 March 2016). "More on Hy and why I think it is a big deal". The Kitchin Research Group. Carnegie Mellon University. Retrieved 19 September 2018.
  8. ^ "Quickstart". hylang.org. 15 May 2018. Retrieved 19 September 2018.

External links[edit]