From f5747bc592f33765cbb5738f049885df6d690de3 Mon Sep 17 00:00:00 2001
From: Arthur de Jong <arthur@arthurdejong.org>
Date: Mon, 20 Jun 2011 20:53:35 +0000
Subject: add an EAN (International Article Number) module

git-svn-id: http://arthurdejong.org/svn/python-stdnum/python-stdnum@70 9dea7c4f-944c-4273-ac1a-574ede026edc
---
 stdnum/__init__.py |  1 +
 stdnum/ean.py      | 50 ++++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 51 insertions(+)
 create mode 100644 stdnum/ean.py

(limited to 'stdnum')

diff --git a/stdnum/__init__.py b/stdnum/__init__.py
index eddc062..f62ba8d 100644
--- a/stdnum/__init__.py
+++ b/stdnum/__init__.py
@@ -27,6 +27,7 @@ Currently this module supports the following formats:
  * ISSN (International Standard Serial Number)
  * ISMN (International Standard Music Number)
  * ISAN (International Standard Audiovisual Number)
+ * EAN (International Article Number)
  * BSN (Burgerservicenummer, the Dutch national identification number)
  * CPF (Cadastro de Pessoas Físicas, the Brazillian national identification
    number)
diff --git a/stdnum/ean.py b/stdnum/ean.py
new file mode 100644
index 0000000..0f1d6fe
--- /dev/null
+++ b/stdnum/ean.py
@@ -0,0 +1,50 @@
+# ean.py - functions for handling EANs
+#
+# Copyright (C) 2011 Arthur de Jong
+#
+# This library is free software; you can redistribute it and/or
+# modify it under the terms of the GNU Lesser General Public
+# License as published by the Free Software Foundation; either
+# version 2.1 of the License, or (at your option) any later version.
+#
+# This library 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
+# Lesser General Public License for more details.
+#
+# You should have received a copy of the GNU Lesser General Public
+# License along with this library; if not, write to the Free Software
+# Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+# 02110-1301 USA
+
+"""Module for handling EAN (International Article Number) codes. This
+module handles numbers EAN-13, EAN-8 and UPC (12-digit) format.
+
+>>> is_valid('73513537')
+True
+>>> is_valid('978-0-471-11709-4') # ISBN-13 format
+True
+"""
+
+def compact(number):
+    """Convert the EAN to the minimal representation. This strips the number
+    of any valid separators and removes surrounding whitespace."""
+    return number.replace(' ','').replace('-','').strip()
+
+def calc_check_digit(number):
+    """Calculate the EAN check digit for 13-digit numbers. The number passed
+    should not have the check bit included."""
+    return str((10 - sum( (3 - 2 * (i % 2)) * int(n) for i, n in enumerate(reversed(number)))) % 10)
+
+def is_valid(number):
+    """Checks to see if the number provided is a valid EAN-13. This checks
+    the length and the check bit but does not check whether a known GS1
+    Prefix and company identifier are referenced."""
+    try:
+        number = compact(number)
+    except:
+        return False
+    return len(number) in (13, 12, 8) and \
+           number.isdigit() and \
+           calc_check_digit(number[:-1]) == number[-1]
+
-- 
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