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This is a validation function for Australian Company Numbers (ACNs). It tests whether the integer or string is a valid ACN (but not whether it is a legal ACN, i.e. if it belongs to the company that is quoting it).

Python, 62 lines
 ``` 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62``` ```def isacn(obj): """isacn(string or int) -> True|False Validate an ACN (Australian Company Number). http://www.asic.gov.au/asic/asic.nsf/byheadline/Australian+Company+Number+(ACN)+Check+Digit Accepts an int, or a string of digits including any leading zeroes. Digits may be optionally separated with spaces. Any other input raises TypeError or ValueError. Return True if the argument is a valid ACN, otherwise False. >>> isacn('004 085 616') True >>> isacn('005 085 616') False """ if isinstance(obj, int): if not 0 <= obj < 10**9: raise ValueError('int out of range for an ACN') obj = '%09d' % obj assert len(obj) == 9 if not isinstance(obj, str): raise TypeError('expected a str or int but got %s' % type(obj)) obj = obj.replace(' ', '') if len(obj) != 9: raise ValueError('ACN must have exactly 9 digits') if not obj.isdigit(): raise ValueError('non-digit found in ACN') digits = [int(c) for c in obj] weights = [8, 7, 6, 5, 4, 3, 2, 1] assert len(digits) == 9 and len(weights) == 8 chksum = 10 - sum(d*w for d,w in zip(digits, weights)) % 10 if chksum == 10: chksum = 0 return chksum == digits[-1] if __name__ == '__main__': # Check the list of valid ACNs from the ASIC website. ACNs = ''' 000 000 019 * 000 250 000 * 000 500 005 * 000 750 005 001 000 004 * 001 250 004 * 001 500 009 * 001 749 999 001 999 999 * 002 249 998 * 002 499 998 * 002 749 993 002 999 993 * 003 249 992 * 003 499 992 * 003 749 988 003 999 988 * 004 249 987 * 004 499 987 * 004 749 982 004 999 982 * 005 249 981 * 005 499 981 * 005 749 986 005 999 977 * 006 249 976 * 006 499 976 * 006 749 980 006 999 980 * 007 249 989 * 007 499 989 * 007 749 975 007 999 975 * 008 249 974 * 008 499 974 * 008 749 979 008 999 979 * 009 249 969 * 009 499 969 * 009 749 964 009 999 964 * 010 249 966 * 010 499 966 * 010 749 961 '''.replace('*', '\n').split('\n') ACNs = [s for s in ACNs if s and not s.isspace()] for s in ACNs: n = int(s.replace(' ', '')) if not (isacn(s) and isacn(n) and not isacn(n+1)): print('test failed for ACN: %s' % s.strip()) break else: print('all ACNs tested okay') ```
 Created by Steven D'Aprano on Fri, 13 May 2011 (MIT)

### Required Modules

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