Add 'python-build-system'.

* guix/build-system/python.scm, guix/build/python-build-system.scm: New files.
* Makefile.am (MODULES): Add them.

guix/build/python-build-system.scm

@@ -0,0 +1,91 @@
+;;; GNU Guix --- Functional package management for GNU
+;;; Copyright © 2013 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013 Nikita Karetnikov <nikita@karetnikov.org>
+;;;
+;;; This file is part of GNU Guix.
+;;;
+;;; GNU Guix is free software; you can redistribute it and/or modify it
+;;; under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation; either version 3 of the License, or (at
+;;; your option) any later version.
+;;;
+;;; GNU Guix is distributed in the hope that it will be useful, but
+;;; WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (guix build python-build-system)
+  #:use-module ((guix build gnu-build-system)
+                #:renamer (symbol-prefix-proc 'gnu:))
+  #:use-module (guix build utils)
+  #:use-module (ice-9 match)
+  #:use-module (ice-9 ftw)
+  #:use-module (srfi srfi-1)
+  #:use-module (srfi srfi-26)
+  #:export (%standard-phases
+            python-build))
+
+;; Commentary:
+;;
+;; Builder-side code of the standard Python package build procedure.
+;;
+;; Code:
+
+(define* (install #:key outputs (configure-flags '())
+                  #:allow-other-keys)
+  "Install a given Python package."
+  (let ((out (assoc-ref outputs "out")))
+    (if (file-exists? "setup.py")
+        (let ((args `("setup.py" "install" ,(string-append "--prefix=" out)
+                      ,@configure-flags)))
+          (format #t "running 'python' with arguments ~s~%" args)
+          (zero? (apply system* "python" args)))
+        (error "no setup.py found"))))
+
+(define* (wrap #:key outputs python-version #:allow-other-keys)
+  (define (list-of-files dir)
+    (map (cut string-append dir "/" <>)
+         (or (scandir dir (lambda (f)
+                            (let ((s (stat (string-append dir "/" f))))
+                              (eq? 'regular (stat:type s)))))
+             '())))
+
+  (define bindirs
+    (append-map (match-lambda
+                 ((_ . dir)
+                  (list (string-append dir "/bin")
+                        (string-append dir "/sbin"))))
+                outputs))
+
+  (let* ((out  (assoc-ref outputs "out"))
+         (var `("PYTHONPATH" prefix
+                ,(cons (string-append out "/lib/python"
+                                      python-version "/site-packages")
+                       (search-path-as-string->list
+                        (or (getenv "PYTHONPATH") ""))))))
+    (for-each (lambda (dir)
+                (let ((files (list-of-files dir)))
+                  (for-each (cut wrap-program <> var)
+                            files)))
+              bindirs)))
+
+(define %standard-phases
+  ;; 'configure' and 'build' phases are not needed.  Everything is done during
+  ;; 'install'.
+  (alist-cons-after
+   'install 'wrap
+   wrap
+   (alist-replace 'install install
+                  (alist-delete 'configure
+                                (alist-delete 'build
+                                              gnu:%standard-phases)))))
+
+(define* (python-build #:key inputs (phases %standard-phases)
+                       #:allow-other-keys #:rest args)
+  "Build the given Python package, applying all of PHASES in order."
+  (apply gnu:gnu-build #:inputs inputs #:phases phases args))
+
+;;; python-build-system.scm ends here