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need simple parsing ability

george young gry at ll.mit.edu
Fri Jul 16 14:52:48 EDT 2004 
On Fri, 16 Jul 2004 17:10:03 GMT
Jean Brouwers <JBrouwersAtProphICyDotCom at no.spam.net> threw this fish to the penguins:
> With two fixes, one bug and one typo:
> 
> ns = '9,foo7-9,2-4,xxx,5, 6, 7, 8, 9, bar, foo_6, foo_10, foo_11'
> 
>  # list of plain, clean names
> ns = [n.strip() for n in ns.split(',')]
>  # expand names with range
> fs = []
> for n in ns:
>     r = n.split('-')
>     if len(r) != 2:  # simple name
>         fs.append(n)
>     else: # name with range
>         h = r[0].rstrip('0123456789')  # header
>         for i in range(int(r[0][len(h):]), 1 + int(r[1])):
>             fs.append(h + str(i))

Mmm, not quite.  If ns=='foo08-11', your fs==[foo8, foo9, foo10, foo11] 
which is wrong.  It should yield  fs==[foo08, foo09, foo10, foo11].
I.e., it must maintain leading zeros in ranges.

(I'm contracting out construction of a special circle of hell for users
who define [foo7, foo08, foo9, foo10] -- they won't be around to complain
that it parses wrong ;-)

> > 
> > In article <20040716111324.09267883.gry at ll.mit.edu>, george young
> > <gry at ll.mit.edu> wrote:
> > 
> > > [python 2.3.3, x86 linux]
> > > For each run of my app, I have a known set of (<100) wafer names.
> > > Names are sometimes simply integers, sometimes a short string, and
> > > sometimes a short string followed by an integer, e.g.:
> > > 
> > >   5, 6, 7, 8, 9, bar, foo_6, foo_7, foo_8, foo_9, foo_10, foo_11
> > > 
> > > I need to read user input of a subset of these.  The user will type a
> > > set of names separated by commas (with optional white space), but there
> > > may also be sequences indicated by a dash between two integers, e.g.: 
> > > 
> > >    "9-11"       meaning 9,10,11
> > >    "foo_11-13"  meaning foo_11, foo_12, and foo_13.
> > >    "foo_9-11"   meaning foo_9,foo_10,foo_11, or 
> > >    "bar09-11"   meaning bar09,bar10,bar11
          ^^^^^^^^            ^^^^^^^^^^^^^^^^^  
> > > (Yes, I have to deal with integers with and without leading zeros)
> > > [I'll proclaim inverse sequences like "foo_11-9" invalid]
> > > So a sample input might be:
> > > 
> > >    9,foo7-9,2-4,xxx   meaning 9,foo7,foo8,foo9,2,3,4,xxx
> > > 
> > > The order of the resultant list of names is not important; I have
> > > to sort them later anyway.
> > > 
> > > Fancy error recovery is not needed; an invalid input string will be
> > > peremptorily wiped from the screen with an annoyed beep.
> > > 
> > > Can anyone suggest a clean way of doing this?  I don't mind
> > > installing and importing some parsing package, as long as my code
> > > using it is clear and simple.  Performance is not an issue.
> > > 
> > > 
> > > -- George Young


-- 
"Are the gods not just?"  "Oh no, child.
What would become of us if they were?" (CSL)
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