multiple replacements

[Steve Holden]

siva1311 at my-deja.com wrote:
> 
> Hi,
> I am a newbie Python programmer and was wondering the best way to make
> multiple replacements of text strings in a file. I have 10-15 strings to
> replace and right now I am doing this like:
> 
>   source = open(source_file,'r')
>   contents = source.read()
>   source.close()
> 
>   contents1 = string.replace(contents, 'foo1', 'bar1')
>   contents2 = string.replace(contents1, 'foo2', 'bar2')
>   ...
>   contents10 = string.replace(contents9, 'foo10', 'bar10')
> 
>   dest = open(dest_file, 'w')
>   dest.write(contents10)
>   dest.close()
> 
> I know this must be a terrible kludge.
> 
Even so, if you only need to do this infrequently it's probably good
enough.  An engineering approach... :-)

> Using sed I can use a single statement to carry out the replacements:
>     sed "s/foo1/bar1/g
>          s/foo2/bar2/g
>          ...
>          s/foo10/bar10/g" source_file > dest_file
> 
> so I assume there must be a much better method than I am currently using
> in my Python version.
> 
> Any suggestions for improvement to the Python code are appreciated.
> 
> -Brad
> 
> Sent via Deja.com http://www.deja.com/
> Before you buy.

Well, there's cleaning the source up and making it easier to extend,
and there's efficiency: you don't say which is your final goal.

You cold clean the source up a bit with:

   foobar = ( ('foo1', 'bar1'),
              ('foo2', 'bar2'),
              ('fooN', 'barN') )
   source = open(source_file,'r')
   contents = source.read()
   source.close()
 
   for foo, bar in foobar:
	contents = replace(contents, foo, bar)
 
   dest = open(dest_file, 'w')
   dest.write(contents10)
   dest.close()

For speedup, you could write the whole loop as a single statement,
but it will get horrible quickly:

   contents = replace(
                 replace(
                 replace(contents,
                 'fooN', 'barN'),
                 'foo2', 'bar2'),
                 'foo1', 'bar1)

and, of course, ths code is much less easy to maintain.

regards
 Steve
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