string.lstrip stripping too much?

[joram gemma]

Hello,

on windows python 2.4.1 I have the following problem

s = 'D:\\music\\D\\ Daniel Lanois\\For the beauty of Wynona'
print s D:\music\D\Dani el Lanois\For the beauty of Wynona t = 'D:\\music\\D\\ '
print t D:\music\D\ s.lstrip(t) 'aniel Lanois\\For the beauty of Wynona'

why does lstrip strip the D of Daniel Lanois also?

thanks in advance
joram

[Roy Smith]

"joram gemma" <jo*********@pa ndora.be> wrote:

Hello,

on windows python 2.4.1 I have the following problem

s = 'D:\\music\\D\\ Daniel Lanois\\For the beauty of Wynona'
print s D:\music\D\Dani el Lanois\For the beauty of Wynona t = 'D:\\music\\D\\ '
print t D:\music\D\ s.lstrip(t) 'aniel Lanois\\For the beauty of Wynona'

why does lstrip strip the D of Daniel Lanois also?

Because the argument to lstrip is a *set of characters* to delete, not a
string to delete. The string you passed it contained a 'D', so the 'D' got
stripped. Imagine lstrip was defined something like:

def lstrip (self, chars):
temp = self
while temp[0] in chars:
temp = temp[1:]
return temp

and you should get the idea. I don't think the documentation for lstrip
really makes this clear. I'm going to open a bug on the doc, and see what
happens :-)

I suspect what you really want to be doing is using the os.path module.
It's got functions for tearing pathnames apart into components, and hides
all the uglyness like whether / or \ is the directory separator on your
particular system.

[Bengt Richter]

On Sun, 15 May 2005 15:24:25 +0200, "joram gemma" <jo*********@pa ndora.be> wrote:

Hello,

on windows python 2.4.1 I have the following problem

s = 'D:\\music\\D\\ Daniel Lanois\\For the beauty of Wynona'
print sD:\music\D\Dan iel Lanois\For the beauty of Wynona t = 'D:\\music\\D\\ '
print tD:\music\D\ s.lstrip(t)'aniel Lanois\\For the beauty of Wynona'
why does lstrip strip the D of Daniel Lanois also?

Because the lstrip argument is a set of characters in the form of
a string, not a single substring to replace from the left. Note:
(repeating your example to start with)

s = 'D:\\music\\D\\ Daniel Lanois\\For the beauty of Wynona'
print s D:\music\D\Dani el Lanois\For the beauty of Wynona t = 'D:\\music\\D\\ '
print t D:\music\D\ s.lstrip(t) 'aniel Lanois\\For the beauty of Wynona'

Now we make an equivalent lstrip argument from your t argument t2 = ''.join(sorted( set(t)))
print t2 :D\cimsu

Note that there is only one of each character in t2 (e.g. 'D' and '\\')
And the result is the same for t and t2:
s.lstrip(t) 'aniel Lanois\\For the beauty of Wynona' s.lstrip(t2)

'aniel Lanois\\For the beauty of Wynona'

If you want to replace an exact prefix, a regex could be a simple way
to get the startswith check and replace in one whack.

Regards,
Bengt Richter

[Dennis Lee Bieber]

On Sun, 15 May 2005 15:24:25 +0200, "joram gemma"
<jo*********@pa ndora.be> declaimed the following in comp.lang.pytho n:

why does lstrip strip the D of Daniel Lanois also?
Because lstrip() does NOT strip a PREFIX string.

The characters you supply, individually, are considered
"strippable ".

help("".lstr ip) Help on built-in function lstrip:

lstrip(...)
S.lstrip([chars]) -> string or unicode

Return a copy of the string S with leading whitespace removed.
If chars is given and not None, remove characters in chars instead.
If chars is unicode, S will be converted to unicode before stripping

lstrip() will remove characters until it finds one that is NOT
IN the argument.
s ="D:\\music\\D\ \Daniel Lanois\\For the beauty of Wynona"
t ="\\Dmscui:"
s.lstrip(t) 'aniel Lanois\\For the beauty of Wynona'
"a" is the first character that does not appear in string t; if you want
to remove a fixed prefix, you need to match on the string itself.
t = "D:\\music\\D\\ "
if s.startswith(t) : .... s = s[len(t):]
.... s 'Daniel Lanois\\For the beauty of Wynona'

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[M.E.Farmer]

Roy Smith:

I suspect what you really want to be doing is using the os.path module. It's got functions for tearing pathnames apart into components, and hides all the uglyness like whether / or \ is the directory separator on your particular system.

I thought so too, maybe this will help.

d = 'D:\\music\\D\\ Daniel Lanois\\For the beauty of Wynona'
import os
os.path.split(d ) ('D:\\music\\D\ \Daniel Lanois', 'For the beauty of Wynona') os.path.basenam e(d) 'For the beauty of Wynona' os.path.dirname (d) 'D:\\music\\D\\ Daniel Lanois' os.path.splitex t(d) ('D:\\music\\D\ \Daniel Lanois\\For the beauty of Wynona', '') os.path.splitdr ive(d) ('D:', '\\music\\D\\Da niel Lanois\\For the beauty of Wynona') os.path.split(d ) ('D:\\music\\D\ \Daniel Lanois', 'For the beauty of Wynona') q = os.path.split(d )
q ('D:\\music\\D\ \Daniel Lanois', 'For the beauty of Wynona') q = os.path.split(q[0])
q ('D:\\music\\D' , 'Daniel Lanois') q = os.path.split(q[0])
q ('D:\\music', 'D')

And another idea might be to do a split using os.sep: import os
d = 'D:\\music\\D\\ Daniel Lanois\\For the beauty of Wynona'
d.split(os.sep)

['D:', 'music', 'D', 'Daniel Lanois', 'For the beauty of Wynona']

Hth,
M.E.Farmer