[Tutor] looping problem

[kumar s]

hi, 

thank you. this is not a homework question. 

I have a very huge file of fasta sequence.

> GeneName xxxxxxxx \t yyyyyyyy
AATTAAGGAAAAAA..........





(1000 lines)
AATAAGGA
>GeneName xxxxxxxx \t yyyyyyyy
GGAGAGAGATTAAGAA
(15000 lines)



when I read this as:

f2= open('myfile','r')
dat = f2.read().split('\n')

turned out to be very expensive deal on computer. 


Instead I tried this:

dat = f2.read() 

(reading into jumbo file of 19,100,442,1342 lines is
easy but getting into what i want is a problem). 


I want to create a dictionary where 'GeneName' as key
and sequence of ATGC characters as value 


biglist = dat.split('\t')
['GeneName xxxxxxxx','yyyyyyyy','ATTAAGGCCAA'.......]

Now I want to select ''GeneName xxxxxxxx' into listA
and 'ATTAAGGCCAA' into listB

so I want to select 0,3,6,9 elements into listA
and 2,5,8,11 and so on elements into listB

then I can do dict(zip(listA,listB))



however, the very loops concept is getting blanked out
in my brain when I want to do this:

for j in range(len(biglist)):
        from here .. I cannot think anything..

may be it is just mental block.. thats the reason I
seek help on forum. 


Thanks





--- jim stockford <jim at well.com> wrote:

> 
> keep a counter in your loop. is this a homework
> question?
> 
> On Sep 23, 2006, at 8:34 AM, kumar s wrote:
> 
> > hi,
> >
> > the reason could be that I did not quite
> understand
> > the concept of looping
> >
> > I have a list of 48 elements
> >
> > I want to create another two lists , listA and
> listB
> >
> > I want to loop through the list with 48 elements
> and
> >
> > select element with index 0,3,6,9,12 ..etc into
> listA
> >
> > select elements with index 2,5,8,11 etc into
> listB.
> >
> >
> > Could any one help me how can I do that
> >
> > thankyou
> >
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> 
> 


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