Update 13Oct2015: Webucator detailed and improved this solution. Take a look!.
North Davidson Street, Naramore Street and Davidson Street, if sorting street names, these streets should be together. However, if these street names are in a list and sorted alphabetically, North Davidson will be placed in with Naramore, nowhere near Davidson in the sort order.
This is the problem posed by a colleage yesterday. To be fair, he had already solved the problem, but it sounded interesting. Giving in to my inner geek, I sat down last night after dinner and figured it out.
For those of you with a short attention span, here is the finished solution.
Breaking this down, the steps are:
Use regular expression (pattern) matching to separate the cardinal direction prefix if present. This first snippet just creates the compiled regular expression.
regex = re.compile( r'(?P<prefix>^North\w*\s|^South\w*\s|^East\w*\s|^West\w*\s|^N\.?\s|^S\.?\s|^E\.?\s|^W\.?\s)?(?P<street>.*)', re.IGNORECASE )
Lower down in the script, the named groups are extracted and converted to lower case to make sure sorting works as expected.
street_match = regex.search(street) if street_match.group('prefix'): street_prefix = street_match.group('prefix') street_root = street_match.group('street')
Create a list of three part tuples consisting of prefix, street name and the original string.
street_sort_list.append((street_prefix, street_root, street))
Sort these tuples first using the street name and if the street name is the same, then the cardinal direction.
street_sort_list.sort(key=itemgetter(1, 0), reverse=False)
Return a list of just the original street name strings sorted based on street name, not the possible direction prefix. This snippet takes advantage of a list comprehension to create this list.
return [street_tuple for street_tuple in street_sort_list]
If you are interested in digging deeper into any of the pieces used to create this function, here are the references I used.
- RegEx Tester: https://regex101.com/#python
- Regular Expression Examples: http://www.pythoncentral.io/more-about-python-regular-expressions/
- Python Sorting: https://wiki.python.org/moin/HowTo/Sorting
- List Comprehensions: https://docs.python.org/2/tutorial/datastructures.html#list-comprehensions
Hopefully you find this useful. At the very least, it does provide an interesting question for problem solving. After completing this, exploring this solution feels not altogether different than a college homework assignment. Although potentially useuful, it did not solve a relevant need for something I need to do. Still, I learned a lot from it! Hence, hopefully you find this page in your search for a real solution and put it to productive use.