python-stdnum commit: r4 - python-stdnum/stdnum

["Commits of the python-stdnum project." <python-stdnum-commits [at] lists.arthurdejong.org>]

Author: arthur
Date: Fri Jul 23 16:46:37 2010
New Revision: 4
URL: http://arthurdejong.org/viewvc/python-stdnum?view=rev&revision=4

Log:
add an ISSN (International Standard Serial Number) module

Added:
   python-stdnum/stdnum/issn.py

Added: python-stdnum/stdnum/issn.py
==============================================================================
--- /dev/null   00:00:00 1970   (empty, because file is newly added)
+++ python-stdnum/stdnum/issn.py        Fri Jul 23 16:46:37 2010        (r4)
@@ -0,0 +1,57 @@
+# issn.py - functions for handling ISSNs
+#
+# Copyright (C) 2010 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 ISSNs (International Standard Serial Number), the
+standard internation code to identify serial publications.
+
+>>> validate('0024-9319')
+True
+>>> validate('0032147X') # incorrect check digit
+False
+>>> compact('0032-1478')
+'00321478'
+>>> format('00249319')
+'0024-9319'
+"""
+
+
+def compact(number):
+    """Convert the ISSN to the minimal representation. This strips the number
+    of any valid ISSN separators and removes surrounding whitespace."""
+    number = number.replace(' ','').replace('-','').strip().upper()
+    return number
+
+def _calc_check_digit(number):
+    """Calculate the ISBN check digit for 10-digit numbers. The number passed
+    should not have the check bit included."""
+    check = (11 - sum( (8 - i) * int(number[i]) for i in range(len(number)) ) 
) % 11
+    return 'X' if check == 10 else str(check)
+
+def validate(number):
+    """Checks to see if the number provided is a valid ISSN. This checks
+    the length and whether the check digit is correct."""
+    number = compact(number)
+    return len(number) == 8 and \
+           number[:-1].isdigit() and \
+           _calc_check_digit(number[:-1]) == number[-1]
+
+def format(number):
+    """Reformat the passed number to the standard format."""
+    number = compact(number)
+    return number[:4] + '-' + number[4:]
--
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