Question on sorting

[Lad]

Hi,
I have a file of records of 4 fields each.
Each field is separated by a semicolon. That is

Filed1;Ffield2; Field3;Field4

But there may be also empty records such as
;;;;
(only semicolons).

For sorting I used
############### ##
lines = file('Config.tx t').readlines() # a file I want to sort
lines.sort()
ff=open('Config Sorted.txt','w' )# sorted file
ff.writelines(l ines)
ff.close()
###############
It was sorted but empty records were first. I need them to be last(at
the end of the file). How can I do that?

Thanks for help
Lad

[wes weston]

Re: Question on sorting

Lad wrote:[color=blue]
> Hi,
> I have a file of records of 4 fields each.
> Each field is separated by a semicolon. That is
>
> Filed1;Ffield2; Field3;Field4
>
> But there may be also empty records such as
> ;;;;
> (only semicolons).
>
> For sorting I used
> ############### ##
> lines = file('Config.tx t').readlines() # a file I want to sort
> lines.sort()
> ff=open('Config Sorted.txt','w' )# sorted file
> ff.writelines(l ines)
> ff.close()
> ###############
> It was sorted but empty records were first. I need them to be last(at
> the end of the file). How can I do that?
>
> Thanks for help
> Lad[/color]

Lad,
The sort call can have a function name as an arg. You
could do:

def mycompare(s1,s2 ):
#return -1 to put s1's at front; 1 to put s1's at back; 0 for a tie
#if s1==";;;;" and s2<>";;;;": return 1

lines.sort(myco mpare)

wes

[Eddie Corns]

Re: Question on sorting

wes weston <wweston@att.ne t> writes:
[color=blue]
>Lad wrote:[color=green]
>> Hi,
>> I have a file of records of 4 fields each.
>> Each field is separated by a semicolon. That is
>>
>> Filed1;Ffield2; Field3;Field4
>>
>> But there may be also empty records such as
>> ;;;;
>> (only semicolons).
>>
>> For sorting I used
>> ############### ##
>> lines = file('Config.tx t').readlines() # a file I want to sort
>> lines.sort()
>> ff=open('Config Sorted.txt','w' )# sorted file
>> ff.writelines(l ines)
>> ff.close()
>> ###############
>> It was sorted but empty records were first. I need them to be last(at
>> the end of the file). How can I do that?
>>
>> Thanks for help
>> Lad[/color][/color]
[color=blue]
>Lad,
> The sort call can have a function name as an arg. You
>could do:[/color]
[color=blue]
>def mycompare(s1,s2 ):
>#return -1 to put s1's at front; 1 to put s1's at back; 0 for a tie
>#if s1==";;;;" and s2<>";;;;": return 1[/color]
[color=blue]
>lines.sort(myc ompare)[/color]

I can't help feeling that the OP might have really wanted to be sorting on
individual fields rather than whole lines. In which case I would think of
doing a line.split(';') on each line before sorting. It would still need
either to use a function to make empty fields go later or alternatively use
DSU (google!) and convert '' to say '~' and back again. This also solves the
problem of what to expect when only some of the fields are blank rather than
all of them.

Eddie

[Lad]

Re: Question on sorting

wes weston <wweston@att.ne t> wrote in message news:<0gKqd.722 52$7i4.43429@bg tnsc05-news.ops.worldn et.att.net>...[color=blue]
> Lad wrote:[color=green]
> > Hi,
> > I have a file of records of 4 fields each.
> > Each field is separated by a semicolon. That is
> >
> > Filed1;Ffield2; Field3;Field4
> >
> > But there may be also empty records such as
> > ;;;;
> > (only semicolons).
> >
> > For sorting I used
> > ############### ##
> > lines = file('Config.tx t').readlines() # a file I want to sort
> > lines.sort()
> > ff=open('Config Sorted.txt','w' )# sorted file
> > ff.writelines(l ines)
> > ff.close()
> > ###############
> > It was sorted but empty records were first. I need them to be last(at
> > the end of the file). How can I do that?
> >
> > Thanks for help
> > Lad[/color]
>
> Lad,
> The sort call can have a function name as an arg. You
> could do:
>
> def mycompare(s1,s2 ):
> #return -1 to put s1's at front; 1 to put s1's at back; 0 for a tie
> #if s1==";;;;" and s2<>";;;;": return 1
>
> lines.sort(myco mpare)
>[/color]
Wes,
Thank you for reply. But I do not understand mycompare function. Can
you please explain to me how it should work? Thanks

LAd

[Peter Otten]

Re: Question on sorting

Lad wrote:
[color=blue]
> wes weston <wweston@att.ne t> wrote in message
> news:<0gKqd.722 52$7i4.43429@bg tnsc05-news.ops.worldn et.att.net>...[color=green]
>> Lad wrote:[color=darkred]
>> > Hi,
>> > I have a file of records of 4 fields each.
>> > Each field is separated by a semicolon. That is
>> >
>> > Filed1;Ffield2; Field3;Field4
>> >
>> > But there may be also empty records such as
>> > ;;;;
>> > (only semicolons).
>> >
>> > For sorting I used
>> > ############### ##
>> > lines = file('Config.tx t').readlines() # a file I want to sort
>> > lines.sort()
>> > ff=open('Config Sorted.txt','w' )# sorted file
>> > ff.writelines(l ines)
>> > ff.close()
>> > ###############
>> > It was sorted but empty records were first. I need them to be last(at
>> > the end of the file). How can I do that?
>> >
>> > Thanks for help
>> > Lad[/color]
>>
>> Lad,
>> The sort call can have a function name as an arg. You
>> could do:
>>
>> def mycompare(s1,s2 ):
>> #return -1 to put s1's at front; 1 to put s1's at back; 0 for a tie
>> #if s1==";;;;" and s2<>";;;;": return 1
>>
>> lines.sort(myco mpare)
>>[/color]
> Wes,
> Thank you for reply. But I do not understand mycompare function. Can
> you please explain to me how it should work? Thanks[/color]

compare(a, b) is just a function for comparing two items/lines. I must
return -1 if a<b, +1 if a>b, and 0 if a==b. For example the following
compare moves the ";;;;" records to the end and keeps the order of others
unaffected:
[color=blue][color=green][color=darkred]
>>> items = [";;;;", ";a;b;;", ";b;a;;", "a;b;c;d;e" , "a;;;d;e"]
>>> def compare(a, b):[/color][/color][/color]
.... return cmp(a == ";;;;", b == ";;;;") or cmp(a, b)
....[color=blue][color=green][color=darkred]
>>> items.sort(comp are)
>>> items[/color][/color][/color]
[';a;b;;', ';b;a;;', 'a;;;d;e', 'a;b;c;d;e', ';;;;']

As Eddie Corns pointed out, you left some doubt whether that is really what
you want. Here is a more complex compare() that handles the lines as
columns split by ";" and puts empty columns last in the sorting order:
[color=blue][color=green][color=darkred]
>>> def key(row):[/color][/color][/color]
.... return [(not col, col) for col in row.split(";")]
....[color=blue][color=green][color=darkred]
>>> def compare(a, b):[/color][/color][/color]
.... return cmp(key(a), key(b))
....[color=blue][color=green][color=darkred]
>>> items.sort(comp are)
>>> items[/color][/color][/color]
['a;b;c;d;e', 'a;;;d;e', ';a;b;;', ';b;a;;', ';;;;']

If you are on Python 2.4, you don't need the compare() detour and can use
key() directly:
[color=blue][color=green][color=darkred]
>>> items.sort(key= key)
>>> items[/color][/color][/color]
['a;b;c;d;e', 'a;;;d;e', ';a;b;;', ';b;a;;', ';;;;']

Finally, the ";;;;" lines don't seem to carry any information - why not
filter them out completely?
[color=blue][color=green][color=darkred]
>>> items = [line[:-1] for line in file("cfg.txt", "U") if line != ";;;;\n"][/color][/color][/color]


Peter

[Lad]

Re: Question on sorting

Peter Otten <__peter__@web. de> wrote in message news:<cokacu$fp 6$04$1@news.t-online.com>...[color=blue]
> Lad wrote:
>[color=green]
> > wes weston <wweston@att.ne t> wrote in message
> > news:<0gKqd.722 52$7i4.43429@bg tnsc05-news.ops.worldn et.att.net>...[color=darkred]
> >> Lad wrote:
> >> > Hi,
> >> > I have a file of records of 4 fields each.
> >> > Each field is separated by a semicolon. That is
> >> >
> >> > Filed1;Ffield2; Field3;Field4
> >> >
> >> > But there may be also empty records such as
> >> > ;;;;
> >> > (only semicolons).
> >> >
> >> > For sorting I used
> >> > ############### ##
> >> > lines = file('Config.tx t').readlines() # a file I want to sort
> >> > lines.sort()
> >> > ff=open('Config Sorted.txt','w' )# sorted file
> >> > ff.writelines(l ines)
> >> > ff.close()
> >> > ###############
> >> > It was sorted but empty records were first. I need them to be last(at
> >> > the end of the file). How can I do that?
> >> >
> >> > Thanks for help
> >> > Lad
> >>
> >> Lad,
> >> The sort call can have a function name as an arg. You
> >> could do:
> >>
> >> def mycompare(s1,s2 ):
> >> #return -1 to put s1's at front; 1 to put s1's at back; 0 for a tie
> >> #if s1==";;;;" and s2<>";;;;": return 1
> >>
> >> lines.sort(myco mpare)
> >>[/color]
> > Wes,
> > Thank you for reply. But I do not understand mycompare function. Can
> > you please explain to me how it should work? Thanks[/color]
>
> compare(a, b) is just a function for comparing two items/lines. I must
> return -1 if a<b, +1 if a>b, and 0 if a==b. For example the following
> compare moves the ";;;;" records to the end and keeps the order of others
> unaffected:
>[color=green][color=darkred]
> >>> items = [";;;;", ";a;b;;", ";b;a;;", "a;b;c;d;e" , "a;;;d;e"]
> >>> def compare(a, b):[/color][/color]
> ... return cmp(a == ";;;;", b == ";;;;") or cmp(a, b)
> ...[color=green][color=darkred]
> >>> items.sort(comp are)
> >>> items[/color][/color]
> [';a;b;;', ';b;a;;', 'a;;;d;e', 'a;b;c;d;e', ';;;;']
>[/color]
Petr,
thank you for help and explanation.
It works
Lad