[Tutor] Fw: list.replace -- string.swap

[ALAN GAULD]

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> From: spir <denis.spir at free.fr>
> To: Alan Gauld <alan.gauld at btinternet.com>
> Sent: Wednesday, 18 March, 2009 8:41:39 AM
> Subject: Re: [Tutor] list.replace -- string.swap
> 
> Le Tue, 17 Mar 2009 20:46:06 -0000,
> "Alan Gauld" s'exprima ainsi:
> > "spir" wrote 
> Sorry, I was unclear all along my post.
> 
> > > Is there a list.replace builtin I cannot find? Or a workaround?
> > 
> > myList[x] = newValue
> > 
> > Or is that too obvious?
> 
> I mean like string.replace. Something like:
> 
> def replace(seq, v1, v2):
>    for (index,item) in enumerate(seq):
>       if item == v1:
>          seq[index] = v2
> 
> Now, I know i does not exist.
> 
> > > Also: How would perform string.swap(s1, s2) in the following cases:
> 
> Here I mean exchanging s1 and s2 occurrences all along a string. As an example, 
> in a text containing numerous formatted numbers, switch from english to european 
> format:
>    1,234,567.89
>    1.234.567,89
> meaning exchange '.' and ','.
> 
> > > * There is no secure 'temp' char, meaning that
> > > s.replace(s1,temp).replace(s2,s1).replace(temp,s2)
> > >  will fail because any char can be part of s.
> 
> The use of a temp char for marking places of one the chars to be swapped is a 
> common trick. But if the text can contain any char (even chr(0)), then there no 
> char you can safely use as temp.
> The only workaround I know is to pass through lists. Then swap on the list, 
> using eg None as temp item, and glue back the result to a string. But you need 
> them a replace method on lists, hence my previous question ;-)
> 
> > > * Either s1 or s2 can be more than a single char.
> 
> More difficult, cause you cannot simple list() the string. It must split on s1 
> and s2, but keeping the delimiters! There is no option afaik for that in 
> string.split -- too bad! So that you must split it manually at start and end of 
> each instance of s1 and s2. Or there are other algorithms I cannot figure out. 
> What I was asking for.
> 
> > Sorry you lost me there. No idea what you mean.
> 
> 
> Sorry, me!
> 
> > Alan G.
> 
> denis
> ------
> la vita e estrany