replacing substrings within strings

[amadain]

Hi
I was wondering if there was a nicer way to swap the first 2
characters in a string with the 4th and 5th characters other than:

darr=list("0102 03040506")
aarr=darr[:2]
barr=darr[4:6]
darr[:2]=barr
darr[4:6]=aarr
result="".join( darr)

The above code works fine but I was wondering if anybody had another
way of doing this?

A

[Diez B. Roggisch]

Re: replacing substrings within strings

amadain wrote:

Hi
I was wondering if there was a nicer way to swap the first 2
characters in a string with the 4th and 5th characters other than:
>
darr=list("0102 03040506")
aarr=darr[:2]
barr=darr[4:6]
darr[:2]=barr
darr[4:6]=aarr
result="".join( darr)
>
The above code works fine but I was wondering if anybody had another
way of doing this?

You can do it like this:


darr=list("0102 03040506")
darr[:2], darr[4:5] = darr[4:6], darr[:2]
result="".join( darr)
print result


Diez

[Rune Strand]

Re: replacing substrings within strings

On Feb 14, 1:08 pm, "amadain" <mfmdev...@gmai l.comwrote:

I was wondering if there was a nicer way to swap the first 2
characters in a string with the 4th and 5th characters other than:
>
darr=list("0102 03040506")
aarr=darr[:2]
barr=darr[4:6]
darr[:2]=barr
darr[4:6]=aarr
result="".join( darr)
>
The above code works fine but I was wondering if anybody had another
way of doing this?

Assuming the string length is always at least 5:

def swap(s):
return '%s%s%s%s' % (s[3:6], s[2:3], s[:2], s[6:])

[amadain]

Re: replacing substrings within strings

On Feb 14, 12:16 pm, "Diez B. Roggisch" <d...@nospam.we b.dewrote:

amadain wrote:

Hi
I was wondering if there was a nicer way to swap the first 2
characters in a string with the 4th and 5th characters other than:

>

darr=list("0102 03040506")
aarr=darr[:2]
barr=darr[4:6]
darr[:2]=barr
darr[4:6]=aarr
result="".join( darr)

>

The above code works fine but I was wondering if anybody had another
way of doing this?

>
You can do it like this:
>
darr=list("0102 03040506")
darr[:2], darr[4:5] = darr[4:6], darr[:2]
result="".join( darr)
print result
>
Diez

Thats the same code. I was wondering if the string manipulation can be
done without an excursion into the list world.

A

[Maric Michaud]

Re: replacing substrings within strings

Le mercredi 14 février 2007 13:08, amadain a écrit :

darr=list("0102 03040506")
aarr=darr[:2]
barr=darr[4:6]
darr[:2]=barr
darr[4:6]=aarr
result="".join( darr)
>
The above code works fine but I was wondering if anybody had another
way of doing this?

Why not :

In [4]: s="010203040506 "

In [5]: print s[4:6] + s[2:4] + s[0:2] + s[6:]
030201040506

?

--
_____________

Maric Michaud
_____________

Aristote - www.aristote.info
3 place des tapis
69004 Lyon
Tel: +33 426 880 097
Mobile: +33 632 77 00 21

[Sion Arrowsmith]

Re: replacing substrings within strings

amadain <mfmdevine@gmai l.comwrote:

>I was wondering if there was a nicer way to swap the first 2
>characters in a string with the 4th and 5th characters other than:
>
>darr=list("010 203040506")
>aarr=darr[:2]
>barr=darr[4:6]
>darr[:2]=barr
>darr[4:6]=aarr
>result="".join (darr)

darr=list("0102 03040506")
darr[:2], darr[4:6] = darr[4:6], darr[:2]
result = "".join(dar r)

--
\S -- siona@chiark.gr eenend.org.uk -- http://www.chaos.org.uk/~sion/
___ | "Frankly I have no feelings towards penguins one way or the other"
\X/ | -- Arthur C. Clarke
her nu becomeþ se bera eadward ofdun hlæddre heafdes bæce bump bump bump

[Rune Strand]

Re: replacing substrings within strings

Or, slighly slower, but more general:

def swap(s, order=(3,4,2,0, 1)):
# assert len(s) >= len(order)
return ''.join([s[o] for o in order]) + s[6:]

[Diez B. Roggisch]

Re: replacing substrings within strings

Thats the same code. I was wondering if the string manipulation can be

done without an excursion into the list world.

That's the price to pay for immutable strings. If you have to to lots of
stuff like that, then keep things a list, and join only when you need the
result as a string.

Diez

[bearophileHUGS@lycos.com]

Re: replacing substrings within strings

Diez B. Roggisch:

That's the price to pay for immutable strings.

Right, but CPython has array.array("c" ) too. Using Diez Roggisch's
code:

>>from array import array
>>arrs = array("c", "0102030405 06")
>>arrs[:2], arrs[4:5] = arrs[4:6], arrs[:2]
>>arrs.tostring ()

'0302013040506'

Using such arrays is useful if you have to do lot of processing before
the final tostring().

Bye,
bearophile

[amadain]

Re: replacing substrings within strings

Thanks all. I usually turn strings into arrays for processing. I was
looking to see if that was the best way to do it from others that use
python. No one else uses python in my company so its nice to get
different points of view from other python users from lists like this.
A

[Diez B. Roggisch]

Re: replacing substrings within strings

bearophileHUGS@ lycos.com wrote:

Diez B. Roggisch:

>That's the price to pay for immutable strings.

>
Right, but CPython has array.array("c" ) too. Using Diez Roggisch's
code:

Ahhh, ze arrayz. I alwayz forget about the arrayz.

Diez

[Paul McGuire]

Re: replacing substrings within strings

On Feb 14, 6:08 am, "amadain" <mfmdev...@gmai l.comwrote:

Hi
I was wondering if there was a nicer way to swap the first 2
characters in a string with the 4th and 5th characters other than:
>
darr=list("0102 03040506")
aarr=darr[:2]
barr=darr[4:6]
darr[:2]=barr
darr[4:6]=aarr
result="".join( darr)
>
The above code works fine but I was wondering if anybody had another
way of doing this?
>
A

"4th and 5th characters" -darr[4:6]

You must be referring to the leading '0' as the 0th character, then.

-- Paul