String Replace only if whole word?

[Juho Schultz]

Michael Yanowitz wrote:
> Hello:
>
>   I am hoping someone knows if there is an easier way to do this or someone
> already implemented something that does this, rather than reinventing the
> wheel:
>   I have been using the string.replace(from_string, to_string, len(string))
> to replace names in a file with their IP address.
>   For example, I have definitions file, that looks something like:
> 10.1.3.4   LANDING_GEAR
> 20.11.222.4   ALTIMETER_100
> 172.18.50.138 SIB
> 172.18.50.138 LAPTOP
> 172.18.51.32  WIN2000
> 127.0.0.1 LOCALHOST
>
>   and I have a text file (a Python script) that has these names in the file.
> In most cases the string.replace() command works great. But there is one
> instance which it fails:
> Suppose I had in the file:
>  if (LAPTOP_IS_UP()):
>    It would replace the string with:
>  if ("172.18.50.138"_IS_UP()):
>
>    Is there any easy way to avoid this, only replace if a whole word
> matches?
> I probably need something which determines when a word ends, and I will
> define
>  a word as containing only 'A'-'Z','a'-'z','0'-'9','_' . As long as the
> string
> contains more of the word digits after the match, don't replace?
>
> Thanks in advance:
> Michael Yanowitz

You need regular expressions for this. Use the re module.
http://docs.python.org/lib/module-re.html

from the docs:

re.sub(pattern, repl, string[, count])
Return the string obtained by replacing the leftmost non-overlapping
occurrences of pattern in string by the replacement repl.

Your pattern would be "[^A-Za-z0-9_]word[^A-Za-z0-9_]"

[^xy] is approximately not in ('x', 'y')

-- 
Juho Schultz