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Re: Python's re module and genealogy problem

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BrJohan wrote:

> On 11/06/2014 14:23, BrJohan wrote:
>> For some genealogical purposes I consider using Python's re module.
>>
>> Rather many names can be spelled in a number of similar ways, and in
>> order to match names even if they are spelled differently, I will build
>> regular expressions, each of which is supposed to match  a number of
>> similar names.
>>
>> I guess that there will be a few hundred such regular expressions
>> covering most popular names.
>>
>> Now, my problem: Is there a way to decide whether any two - or more - of
>> those regular expressions will match the same string?
>>
>> Or, stated a little differently:
>>
>> Can it, for a pair of regular expressions be decided whether at least
>> one string matching both of those regular expressions, can be
>> constructed?
>>
>> If it is possible to make such a decision, then how? Anyone aware of an
>> algorithm for this?
> 
> Thank you all for valuable input and interesting thoughts.
> 
> After having reconsidered my problem, it might be better to approach it
> a little differently.
> 
> Either to state the regexps simply like:
> "(Kristina)|(Christina)|(Cristine)|(Kristine)"
> instead of "((K|(Ch))ristina)|([CK]ristine)"
> 
> Or to put the namevariants in some sequence of sets having elements like:
> ("Kristina", "Christina", "Cristine", "Kristine")
> Matching is then just applying the 'in' operator.
> 
> I see two distinct advantages.
> 1. Readability and maintainability
> 2. Any namevariant occurring in just one regexp or set means no risk of
> erroneous matching.
> 
> Comments?

I like the simple variant

kristinas = ("Kristina", "Christina", "Cristine", "Kristine")

But instead of matching with "in" you could build a dict that maps the name 
variants to a normalised name

normalized_names = {
    "Kristina": "Kristina",
    "Christina": "Kristina",
    ...
    "John": "John",
    "Johann": "John",
    ...
}
def normalized(name):
    return normalized_names.get(name, name)

If you put persons in another dict or a database indexed by the normalised 
name 

lookup = {
    "Kristina": ["Kristina Smith", "Christina Miller"],
    ...
}

you can find all Kristinas with two look-ups:

>>> lookup[normalized("Kristine")]
['Kristina Smith', 'Christina Miller']

PS: A problem with this approach might be that (name in nameset_A) and (name 
in nameset_B) implies nameset_A == nameset_B

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Python's re module and genealogy problem BrJohan <brjohan@gmail.com> - 2014-06-11 14:23 +0200
  Re: Python's re module and genealogy problem Robert Kern <robert.kern@gmail.com> - 2014-06-11 14:26 +0100
    Re: Python's re module and genealogy problem Mark H Harris <harrismh777@gmail.com> - 2014-06-11 09:08 -0500
  Re: Python's re module and genealogy problem Thomas Rachel <nutznetz-0c1b6768-bfa9-48d5-a470-7603bd3aa915@spamschutz.glglgl.de> - 2014-06-11 15:55 +0200
  Re: Python's re module and genealogy problem Michael Torrie <torriem@gmail.com> - 2014-06-11 09:34 -0600
  Re: Python's re module and genealogy problem Nick Cash <nick.cash@npcinternational.com> - 2014-06-11 16:21 +0000
  Re: Python's re module and genealogy problem Simon Ward <simon@bleah.co.uk> - 2014-06-11 18:21 +0100
  Re: Python's re module and genealogy problem Vlastimil Brom <vlastimil.brom@gmail.com> - 2014-06-11 20:09 +0200
  Re: Python's re module and genealogy problem BrJohan <brjohan@gmail.com> - 2014-06-13 17:17 +0200
    Re: Python's re module and genealogy problem Peter Otten <__peter__@web.de> - 2014-06-13 18:26 +0200
    Re: Python's re module and genealogy problem Dan Sommers <dan@tombstonezero.net> - 2014-06-14 05:14 +0000
  Re: Python's re module and genealogy problem Tony the Tiger <tony@tiger.invalid> - 2014-06-14 08:35 +0000

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