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Re: lstrip problem - beginner question

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From Peter Otten <__peter__@web.de>
Subject Re: lstrip problem - beginner question
Date Tue, 04 Jun 2013 17:52:37 +0200
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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?

"abba".lstrip("ab")

does not remove the prefix "ab" from the string "abba". Instead it removes 
chars from the beginning until it encounters one that is not in "ab". So

t = s.lstrip(chars_to_be_removed)

is roughly equivalent to

t = s
while len(t) > 0 and t[0] in chars_to_be_removed:
    t = t[1:]

If you want to remove a prefix use

s = "abba"
prefix = "ab"
if s.startswith(prefix):
    s = s[len(prefix):]

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Thread

lstrip problem - beginner question mstagliamonte <madmaxthc@yahoo.it> - 2013-06-04 08:21 -0700
  Re: lstrip problem - beginner question mstagliamonte <madmaxthc@yahoo.it> - 2013-06-04 08:24 -0700
  Re: lstrip problem - beginner question mstagliamonte <madmaxthc@yahoo.it> - 2013-06-04 08:25 -0700
    Re: lstrip problem - beginner question Fábio Santos <fabiosantosart@gmail.com> - 2013-06-04 16:41 +0100
      Re: lstrip problem - beginner question mstagliamonte <madmaxthc@yahoo.it> - 2013-06-04 08:49 -0700
        Re: lstrip problem - beginner question Mark Lawrence <breamoreboy@yahoo.co.uk> - 2013-06-04 17:01 +0100
        Re: lstrip problem - beginner question Dave Angel <davea@davea.name> - 2013-06-04 17:48 -0400
  Re: lstrip problem - beginner question mstagliamonte <madmaxthc@yahoo.it> - 2013-06-04 08:28 -0700
  Re: lstrip problem - beginner question mstagliamonte <madmaxthc@yahoo.it> - 2013-06-04 08:29 -0700
  Re: lstrip problem - beginner question MRAB <python@mrabarnett.plus.com> - 2013-06-04 16:48 +0100
    Re: lstrip problem - beginner question mstagliamonte <madmaxthc@yahoo.it> - 2013-06-04 08:53 -0700
  Re: lstrip problem - beginner question Peter Otten <__peter__@web.de> - 2013-06-04 17:52 +0200
  Re: lstrip problem - beginner question John Gordon <gordon@panix.com> - 2013-06-04 15:55 +0000
    Re: lstrip problem - beginner question mstagliamonte <madmaxthc@yahoo.it> - 2013-06-04 09:06 -0700
  Re: lstrip problem - beginner question Larry Hudson <orgnut@yahoo.com> - 2013-06-04 21:53 -0700

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