[BangPypers] chaining string operations..

[Vishal]

On Fri, Mar 25, 2011 at 5:45 PM, Vishal <vsapre80 at gmail.com> wrote:

> On Fri, Mar 25, 2011 at 3:31 PM, Senthil Kumaran <orsenthil at gmail.com>wrote:
>
>> On Fri, Mar 25, 2011 at 03:22:02PM +0530, Vishal wrote:
>>
>> > I have a string that can be many megabytes worth memory size, and i
>> > want to
>>
>> If you have got that string from a file like object, instead of
>> loading the entire string in memory you could iterate through the file
>> object to load one line at time. This will help provided the string is
>> has line-separators.
>>
>> Otherwise you could store in a mock StringIO file like object and
>> iterate, if the string is heavy to handle in memory.
>>
>> >
>> > Now I would like to chain these replacements into something like this:
>> >
>> > >>> s1 = s.replacements((' a', 'S'), (' \t', '\n'), ('C#', '\n')))
>> >
>> > Is there a known way of doing this currently in Python, apart from
>> producing
>>
>> Here is one recipe to do multiple string replacement in python in a
>> single shot.
>>
>>
>> http://uthcode.sarovar.org/pycon2010/strings.html#making-multiple-replacements-in-a-string-in-a-single-pass
>>
>> --
>> Senthil
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>>
>
> Thanks for his one. This is what I was looking for.
>
> --
> Thanks and best regards,
> Vishal Sapre
>

Hi,

Just realized after using the above solution :
http://uthcode.sarovar.org/pycon2010/strings.html#making-multiple-replacements-in-a-string-in-a-single-pass

def multiple_replace(text, adict):
    rx = re.compile('|'.join(map(re.escape, adict)))

    def one_xlat(match):
        return adict[match.group(0)]

    return rx.sub(one_xlat, text)

that *this one is not* what I was looking for.

The use of '|' character in the regular expression, makes sure that the
sequence of replacements is not preserved, which is exactly what I want to
avoid.

Is there another way to making (compiling) the regex such that match happens
as per a given sequence, and not as per occurrence of pattern in the given
string.

-- 
Thanks and best regards,
Vishal Sapre