Re: Needed: a tidy model for varying numbers of multiple numerical values (page number refs)?

2009-03-10 Thread Dave E 

First, thanks for the responses. Second, to answer the questions:

1.
> - how would you like to handle (or not-handle) overlapping
> ranges?  ("100 ..150, 120, 145-155")

as above, in order, lowest number in range first

2.
> - are ranges always specified the same way? (".." vs. "-")

According to what works best, they will be specified either .. or -
but not both. I prefer the .. (from Perl and Ruby) but I know it isn't
used in Python.

3.
> - do you need to be able to sort the contents by page number?
> (and how does that interplay with overlapping ranges if allowed?)

yes, and see 1 above

4.
> - do you need to be able to find whether a given page is within the range of 
> listed pages?

no

5.
> - are page numbers always integers?  (think Roman numerals used
> in pre-text matter, or appendices with page numbers like "B-13")

at the moment, yes, but good reminder to think of a more flexible
solution - they may not always be. For now - i.e. my immediate need -
they are always numerical (apart from the range separator .. or - )

> A couple thoughts occur to me:
>
[snip example]
>
> Granted, many of these bits may not matter to you, but if you need the 
> flexibility of any of them, the others come for free.
>
> Just a few pre-breakfast rambling thoughts...

It'll be a few days at least before I get back to the project (my
first real-world site in Django), so I'll check back here forst and
implement the above if nothing else is suggested. Thanks again :-)

- Dave
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Re: Needed: a tidy model for varying numbers of multiple numerical values (page number refs)?

2009-03-09 Thread Alex Gaynor 
On Mon, Mar 9, 2009 at 5:02 AM, Tim Chase wrote:

>
> Dave E wrote:
> > I have some data (page number references) that looks like this:
> >
> > 320, 387..90, 410, 500
> >
> > or (sustituting numerical .. ranges for conventional dashes)
> >
> > 320, 387-90, 410, 500, 634
> >
> > I'd just like to know the most Django-esque way of creating a model
> > for these?
> >
> > The requirements are:
> >
> > 1. they're all numbers, or ranges of numbers
> >
> > 2. there will be at least one - and an unknown number of other - page
> > numbers or ranges, but not more than (say) 30.
> >
> > I've looked through a lot of documentation (and custom fields), but
> > can't find a tidy solution. I know that SET is a MySQL enxtension, so
> > not handled by Django.
> >
> > The issue has to be related to that of creating a model for HTML meta
> > tags, except that these are all numbers or number ranges.
>
> There are some other details you omit:
>
> - how would you like to handle (or not-handle) overlapping
> ranges?  ("100..150, 120, 145-155")
>
> - are ranges always specified the same way? (".." vs. "-")
>
> - do you need to be able to sort the contents by page number?
> (and how does that interplay with overlapping ranges if allowed?)
>
> - do you need to be able to find whether a given page is within
> the range of listed pages?
>
> - are page numbers always integers?  (think Roman numerals used
> in pre-text matter, or appendices with page numbers like "B-13")
>
> A couple thoughts occur to me:
>
> 1) just use a regexp-field and store them as a text-field (since
> you have a predefined cap of 30 you can get a rough estimate of a
> max...3 chars + 2 range characters + 3 chars + 1 comma + 1 space
> = 10 chars per range, * 30 references = 300 chars).  This allows
> for a small bit of validation, but doesn't offer much flexibility
> in terms of sorting/searching/overlaps.  It does allow for the
> Roman/appendix numbering scheme, depending on how tight you make
> your regexp
>
> 2) create a model like
>
>class PageRange(Model):
>  source = ForeignKey(SomeOtherModel)
>  start = PositiveIntegerField()
>  end = PositiveIntegerField()
>  def __repr__(self):
>if self.end:
>  if self.end > self.start:
>return "%s-%s" % (self.start, self.end)
>  elif self.end < self.start:
>return "INVERTED RANGE [%s-%s]" % (
>  self.start, self.end)
>return str(self.start)
>
> then perhaps do some population/checks on the save (start must be
> <= end; if end is Null, default to start; perhaps check for
> pre-existing ranges and see if these bounds fall within another
> one).  This has advantages that you can sort them, perform better
> checks on them, querying against them is easier, you can
> aggregate them to find the count, and you're not limited to an
> arbitrary number like 30.  Granted, many of these bits may not
> matter to you, but if you need the flexibility of any of them,
> the others come for free.
>
> Just a few pre-breakfast rambling thoughts...
>
> -tim
>
>
>
>
>
>
>
> >
>
I agree with Tim, the relational way to handle this is a seperate model that
stores individual page ranges.

Alex

-- 
"I disapprove of what you say, but I will defend to the death your right to
say it." --Voltaire
"The people's good is the highest law."--Cicero

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Re: Needed: a tidy model for varying numbers of multiple numerical values (page number refs)?

2009-03-09 Thread Tim Chase 

Dave E wrote:
> I have some data (page number references) that looks like this:
> 
> 320, 387..90, 410, 500
> 
> or (sustituting numerical .. ranges for conventional dashes)
> 
> 320, 387-90, 410, 500, 634
> 
> I'd just like to know the most Django-esque way of creating a model
> for these?
> 
> The requirements are:
> 
> 1. they're all numbers, or ranges of numbers
> 
> 2. there will be at least one - and an unknown number of other - page
> numbers or ranges, but not more than (say) 30.
> 
> I've looked through a lot of documentation (and custom fields), but
> can't find a tidy solution. I know that SET is a MySQL enxtension, so
> not handled by Django.
> 
> The issue has to be related to that of creating a model for HTML meta
> tags, except that these are all numbers or number ranges.

There are some other details you omit:

- how would you like to handle (or not-handle) overlapping 
ranges?  ("100..150, 120, 145-155")

- are ranges always specified the same way? (".." vs. "-")

- do you need to be able to sort the contents by page number? 
(and how does that interplay with overlapping ranges if allowed?)

- do you need to be able to find whether a given page is within 
the range of listed pages?

- are page numbers always integers?  (think Roman numerals used 
in pre-text matter, or appendices with page numbers like "B-13")

A couple thoughts occur to me:

1) just use a regexp-field and store them as a text-field (since 
you have a predefined cap of 30 you can get a rough estimate of a 
max...3 chars + 2 range characters + 3 chars + 1 comma + 1 space 
= 10 chars per range, * 30 references = 300 chars).  This allows 
for a small bit of validation, but doesn't offer much flexibility 
in terms of sorting/searching/overlaps.  It does allow for the 
Roman/appendix numbering scheme, depending on how tight you make 
your regexp

2) create a model like

class PageRange(Model):
  source = ForeignKey(SomeOtherModel)
  start = PositiveIntegerField()
  end = PositiveIntegerField()
  def __repr__(self):
if self.end:
  if self.end > self.start:
return "%s-%s" % (self.start, self.end)
  elif self.end < self.start:
return "INVERTED RANGE [%s-%s]" % (
  self.start, self.end)
return str(self.start)

then perhaps do some population/checks on the save (start must be 
<= end; if end is Null, default to start; perhaps check for 
pre-existing ranges and see if these bounds fall within another 
one).  This has advantages that you can sort them, perform better 
checks on them, querying against them is easier, you can 
aggregate them to find the count, and you're not limited to an 
arbitrary number like 30.  Granted, many of these bits may not 
matter to you, but if you need the flexibility of any of them, 
the others come for free.

Just a few pre-breakfast rambling thoughts...

-tim







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Needed: a tidy model for varying numbers of multiple numerical values (page number refs)?

2009-03-09 Thread Dave E 

I have some data (page number references) that looks like this:

320, 387..90, 410, 500

or (sustituting numerical .. ranges for conventional dashes)

320, 387-90, 410, 500, 634

I'd just like to know the most Django-esque way of creating a model
for these?

The requirements are:

1. they're all numbers, or ranges of numbers

2. there will be at least one - and an unknown number of other - page
numbers or ranges, but not more than (say) 30.

I've looked through a lot of documentation (and custom fields), but
can't find a tidy solution. I know that SET is a MySQL enxtension, so
not handled by Django.

The issue has to be related to that of creating a model for HTML meta
tags, except that these are all numbers or number ranges.

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