[Tutor] Question on regular expressions

[Karl Pflästerer]

On 24 Mai 2006, andrew.arobert at gmail.com wrote:

> I have two Perl expressions
>
>
> If windows:
>
> perl -ple "s/([^\w\s])/sprintf(q#%%%2X#, ord $1)/ge"  somefile.txt
>
> If posix
>
> perl -ple 's/([^\w\s])/sprintf("%%%2X", ord $1)/ge'  somefile.txt
>
>
>
> The [^\w\s]  is a negated expression stating that any character
> a-zA-Z0-9_, space or tab is ignored.
>
> The () captures whatever matches and throws it into the $1 for
> processing by the sprintf
>
> In this case, %%%2X which is a three character hex value.
>
> How would you convert this to a python equivalent using the re or
> similar module?

python -c "import re, sys;print re.sub(r'([^\w\s])', lambda s: '%%%2X' % ord(s.group()), sys.stdin.read())," < somefile

It's not as short as the Perl version (and might have problems with big
files). Python does not have such useful command line switches like -p
(but you doesn't use Python so much for one liners as Perl) but it does
the same ; at least in this special case (Python lacks something like the
-l switch).

With bash it's a bit easier. (maybe there's also a way with cmd.com to
write multiple lines)?

$ python -c "import re,sys
for line in sys.stdin: print re.sub(r'([^\w\s])', lambda s: '%%%2X' % ord(s.group()), line)," < somefile


   Karl
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