lstrip problem - beginner question

[Fábio Santos]

On 4 Jun 2013 16:34, "mstagliamonte" <madmaxthc at yahoo.it> wrote:
>
> On Tuesday, June 4, 2013 11:21:53 AM UTC-4, mstagliamonte wrote:
> > Hi everyone,
> >
> >
> >
> > I am a beginner in python and trying to find my way through... :)
> >
> >
> >
> > I am writing a script to get numbers from the headers of a text file.
> >
> >
> >
> > If the header is something like:
> >
> > h01 = ('>scaffold_1')
> >
> > I just use:
> >
> > h01.lstrip('>scaffold_')
> >
> > and this returns me '1'
> >
> >
> >
> > But, if the header is:
> >
> > h02: ('>contig-100_0')
> >
> > if I use:
> >
> > h02.lstrip('>contig-100_')
> >
> > this returns me with: ''
> >
> > ...basically nothing. What surprises me is that if I do in this other
way:
> >
> > h02b = h02.lstrip('>contig-100')
> >
> > I get h02b = ('_1')
> >
> > and subsequently:
> >
> > h02b.lstrip('_')
> >
> > returns me with: '1' which is what I wanted!
> >
> >
> >
> > Why is this happening? What am I missing?
> >
> >
> >
> > Thanks for your help and attention
> >
> > Max
>
> edit: h02: ('>contig-100_1')

You don't have to use ('..') to declare a string. Just 'your string' will
do.

You can use str.split to split your string by a character.

(Not tested)

string_on_left, numbers = '>contig-100_01'.split('-')
left_number, right_number = numbers.split('_')
left_number, right_number = int(left_number), int(right_number)

Of course, you will want to replace the variable names.

If you have more advanced parsing needs, you will want to look at regular
expressions or blobs.
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