invert the order of a string

[rtilley]

s = list('some_random_string')
print s
s.reverse()
print s
s = ''.join(s)
print s

Surely there's a better way to do this, right?

[Dave Hansen]

On Mon, 13 Feb 2006 18:51:11 +0000 in comp.lang.python, rtilley
<rt*****@vt.edu> wrote:

s = list('some_random_string')
print s
s.reverse()
print s
s = ''.join(s)
print s

Surely there's a better way to do this, right?

How about

s = "some random string"
print s
s = s[::-1]
print s

HTH,
-=Dave
-=Dave

--
Change is inevitable, progress is not.

[rtilley]

Dave Hansen wrote:

How about

s = "some random string"
print s
s = s[::-1]
print s

That looks like Perl, but it works. Makes me wonder with the string
module doesn't have a reverse or invert function?

[Paul Rubin]

rtilley <rt*****@vt.edu> writes:

s = list('some_random_string')
print s
s.reverse()
print s
s = ''.join(s)
print s

Surely there's a better way to do this, right?

In Python 2.4, just say
s = reversed('some_random_string')

[Dave Hansen]

On Mon, 13 Feb 2006 19:03:32 +0000 in comp.lang.python, rtilley
<rt*****@vt.edu> wrote:

Dave Hansen wrote:

How about

s = "some random string"
print s
s = s[::-1]
print s

That looks like Perl, but it works. Makes me wonder with the string
module doesn't have a reverse or invert function?

It's just simple slicing. Well, maybe not so simple, or at least not
so common, but with a syntax similar to the range function. Consider
the following (string chosen to make it obvious what's going on):

s = "0123456789"
s[::]
s[3::]
s[:3:]
s[::3]
s[::-2]
s[-2::-2]

Regards,
-=Dave

--
Change is inevitable, progress is not.

[rtilley]

Dave Hansen wrote:

It's just simple slicing. Well, maybe not so simple, or at least not
so common, but with a syntax similar to the range function. Consider
the following (string chosen to make it obvious what's going on):

s = "0123456789"
s[::]
s[3::]
s[:3:]
s[::3]
s[::-2]
s[-2::-2]

Well, it turns out to be the best way to invert a string, IMO. The
reversed() feature returns a reversed object... not a reversed string.
In short, I have to fool with it again _after_ it has been inverted. The
slicing takes care of the job right away and gives me what I want... no
Computer Sciencey <reversed object at 0xb6f6152c>> to deal with :)

I'm sure the reversed feature is much more generic though for dealing
with other types.

[Bruno Desthuilliers]

rtilley a écrit :

s = list('some_random_string')
print s
s.reverse()
print s
s = ''.join(s)
print s

Surely there's a better way to do this, right?

print 'some_random_string'[::-1]

[Bruno Desthuilliers]

Paul Rubin a écrit :

rtilley <rt*****@vt.edu> writes:

s = list('some_random_string')
print s
s.reverse()
print s
s = ''.join(s)
print s

Surely there's a better way to do this, right?

In Python 2.4, just say
s = reversed('some_random_string')

Python 2.4.1 (#1, Jul 23 2005, 00:37:37)
[GCC 3.3.4 20040623 (Gentoo Linux 3.3.4-r1, ssp-3.3.2-2, pie-8.7.6)] on
linux2
Type "help", "copyright", "credits" or "license" for more information.

reversed('some_random_string') <reversed object at 0x4040f30c>

Yes, that was my first take too - but I jumped to my Python shell before
posting !-)

[Paul Rubin]

rtilley <rt*****@vt.edu> writes:

Well, it turns out to be the best way to invert a string, IMO. The
reversed() feature returns a reversed object... not a reversed
string. In short, I have to fool with it again _after_ it has been
inverted. The slicing takes care of the job right away and gives me
what I want... no Computer Sciencey <reversed object at 0xb6f6152c>>
to deal with :)

Oh, I see. I thought I'd tested reversed(...) but I guess I didn't.
I'm going senile. reversed makes an iterator.

Anyway, slicing is one solution; the array module is another.

[Eric McGraw]

> Well, it turns out to be the best way to invert a string, IMO. The

reversed() feature returns a reversed object... not a reversed string.
In short, I have to fool with it again _after_ it has been inverted. The
slicing takes care of the job right away and gives me what I want... no
Computer Sciencey <reversed object at 0xb6f6152c>> to deal with :)
A <reversed object> can be turned back into a string:

st = '0123456789'
reversed(st) <reversed object at 0x00A8CC50> ''.join( reversed(st) )

'9876543210'

I'm sure the reversed feature is much more generic though for dealing
with other types.

[Carl Cerecke]

Eric McGraw wrote:

Well, it turns out to be the best way to invert a string, IMO. The
reversed() feature returns a reversed object... not a reversed string.
In short, I have to fool with it again _after_ it has been inverted. The
slicing takes care of the job right away and gives me what I want... no
Computer Sciencey <reversed object at 0xb6f6152c>> to deal with :)

A <reversed object> can be turned back into a string:

>>> st = '0123456789'
>>> reversed(st) <reversed object at 0x00A8CC50> >>> ''.join( reversed(st) )

'9876543210'

But that's slower than new_s = s[::-1]

Cheers,
Carl.