manipulate string

[Chris]

I heard that strings are immutable, but isn't there regardless a way to
manipulate a string?
I have a string that looks like this:
a = '0123456789'
But I want it to look like this:
a = '0 - 2 - 4 - 6 - 8 - '
I want whitespace between every number and I want to fade out every
second number.
It is funny that I can explicitly read parts of that string, print a[3]
works perfectly, but I can't remove it, delete it or what ever.

I would appreciate any hint on how to solve my little "problem".

Thanks a lot.
Regards, Tom

[Michel Claveau/Hamster]

Re: manipulate string

Like this :


import string

a='0123456789'
l=list(a)
b=string.join(l ,' - ')
print b



@-salutations
--
Michel Claveau
mél : http://cerbermail.com/?6J1TthIa8B

[Eric Brunel]

Re: manipulate string

Michel Claveau/Hamster wrote:[color=blue]
> Like this :
>
>
> import string
>
> a='0123456789'
> l=list(a)
> b=string.join(l ,' - ')
> print b[/color]

Apparently, the OP wants to discard characters at indexes 1, 3, 5, 7, etc... So,
assuming Python version is 2.3, the correct solution seems to be:
[color=blue][color=green][color=darkred]
>>> a='0123456789'
>>> print ' - '.join(a[::2])[/color][/color][/color]
0 - 2 - 4 - 6 - 8

HTH
--
- Eric Brunel <eric dot brunel at pragmadev dot com> -
PragmaDev : Real Time Software Development Tools - http://www.pragmadev.com

[Michel Claveau/Hamster]

Re: manipulate string

Oups ! Sorry, i had read too fast...

[Michel Claveau/Hamster]

Re: manipulate string

2 by 2 :


import string
a='0123456789'
l=list(a[::2])
b=string.join(l ,' - ')
print b

[Chris]

Re: manipulate string

Thanks guys.
I knew it couldn't be too difficult, but I just didn't know in which
direction I should search for a solution. :-)

Thanks again.
Regards, Tom

[Chris]

Re: manipulate string

It is me again.
Unfortunately it doesn't work. Python doesn't accept [::2]
TypeError: sequence index must be integer
I use Python Release 2.2.3.
Any ideas?

-Tom

[David C. Fox]

Re: manipulate string

> import string[color=blue]
> a='0123456789'
> l=list(a[::2])
> b=string.join(l ,' - ')
> print b[/color]

Chris wrote:
[color=blue]
> It is me again.
> Unfortunately it doesn't work. Python doesn't accept [::2]
> TypeError: sequence index must be integer
> I use Python Release 2.2.3.
> Any ideas?
>
> -Tom
>[/color]

Yeah, the x[::i] notation for strings and lists only works in 2.3.

A couple of alternatives to l = list(a[::2]) which work in 2.2 are:

l = []
for i in range( (len(a) + 1) // 2):
l.append(a[2*i])

or more compactly

l=[a[2*i] for i in range((len(a)+1 )//2)]

or

l = [a[i] for i in range(len(a)) if 2*(i//2) == i]

David

[David C. Fox]

Re: manipulate string

David C. Fox wrote:
[color=blue][color=green]
>> import string
>> a='0123456789'
>> l=list(a[::2])
>> b=string.join(l ,' - ')
>> print b[/color]
>
>
> Chris wrote:
>[color=green]
>> It is me again.
>> Unfortunately it doesn't work. Python doesn't accept [::2]
>> TypeError: sequence index must be integer
>> I use Python Release 2.2.3.
>> Any ideas?
>>
>> -Tom
>>[/color]
>
> Yeah, the x[::i] notation for strings and lists only works in 2.3.
>
> A couple of alternatives to l = list(a[::2]) which work in 2.2 are:
>
> l = []
> for i in range( (len(a) + 1) // 2):
> l.append(a[2*i])
>
> or more compactly
>
> l=[a[2*i] for i in range((len(a)+1 )//2)]
>
> or
>
> l = [a[i] for i in range(len(a)) if 2*(i//2) == i]
>
> David
>[/color]

or

l = [a[i] for i in range(0, len(a), 2)]

David

[Werner Schiendl]

Re: manipulate string

Hi,

Eric Brunel wrote:[color=blue]
>
> Apparently, the OP wants to discard characters at indexes 1, 3, 5, 7,
> etc... So, assuming Python version is 2.3, the correct solution seems to
> be:
>[color=green][color=darkred]
> >>> a='0123456789'
> >>> print ' - '.join(a[::2])[/color][/color]
> 0 - 2 - 4 - 6 - 8
>[/color]

almost :-)

the original poster said he wanted

a = '0 - 2 - 4 - 6 - 8 - '

which means the last faded-out 9 is missing in your solution


the following works:
[color=blue][color=green][color=darkred]
>>> a = '0123456789'
>>>
>>> b = " ".join( [i % 2 and "-" or a[i] for i in range(len(a))] )
>>> b[/color][/color][/color]
'0 - 2 - 4 - 6 - 8 -'


I think the trailing space is a typo of the OP...


hth

Werner

[Werner Schiendl]

Re: manipulate string

Hi,

Werner Schiendl wrote:
[color=blue]
>
> the following works:
>[color=green][color=darkred]
> >>> a = '0123456789'
> >>>
> >>> b = " ".join( [i % 2 and "-" or a[i] for i in range(len(a))] )
> >>> b[/color][/color]
> '0 - 2 - 4 - 6 - 8 -'
>
>[/color]

if you prefer to use generators, you could use:
[color=blue][color=green][color=darkred]
>>> a = '0123456789'
>>>
>>> def hide_every_2nd( x):[/color][/color][/color]
.... while True:
.... yield x.next()
.... x.next()
.... yield "-"
....[color=blue][color=green][color=darkred]
>>> b = " ".join(hide_eve ry_2nd(iter(a)) )
>>> b[/color][/color][/color]
'0 - 2 - 4 - 6 - 8 -'


hth

Werner

[Inyeol Lee]

Re: manipulate string

On Tue, Oct 28, 2003 at 07:06:36PM +0100, Chris wrote:[color=blue]
> It is me again.
> Unfortunately it doesn't work. Python doesn't accept [::2]
> TypeError: sequence index must be integer
> I use Python Release 2.2.3.
> Any ideas?[/color]

Then,
[color=blue][color=green][color=darkred]
>>> s = "0123456789 "
>>> " - ".join([s[i] for i in range(0, 10, 2)])[/color][/color][/color]
'0 - 2 - 4 - 6 - 8'

-Inyeol

[Chris]

Re: manipulate string

Thanks for all the help.
I just decided to update to Python 2.3 anyway.

Thanks to all, Tom

[Skip Montanaro]

Re: manipulate string

[color=blue][color=green][color=darkred]
>>> s = "0123456789 "
>>> " - ".join([s[i] for i in range(0, 10, 2)])[/color][/color][/color]
'0 - 2 - 4 - 6 - 8'

I thought the original poster wanted the odd numbers replaced by '-' and then
all elements separated by spaces. None of the ' - '.join(...) examples
achieve that, as they fail to replace '9' with '-'. Here's an alternative
which does:
[color=blue][color=green][color=darkred]
>>> s = "0123456789 "
>>> [int(c)%2 and '-' or c for c in s][/color][/color][/color]
['0', '-', '2', '-', '4', '-', '6', '-', '8', '-'][color=blue][color=green][color=darkred]
>>> ' '.join([int(c)%2 and '-' or c for c in s])[/color][/color][/color]
'0 - 2 - 4 - 6 - 8 -'

Skip

[Michel Claveau/Hamster]

Re: manipulate string

LOL