support regex search/replace within columns

[pstoll]

I've implemented an initial extension to csvgrep that allows specifying a search regex pattern and a replacement string (including references to groups via the regex pattern).

So as an example, given a CSV, this modifies column 1 by doing a
re.sub('-s flag', '-x flag', 'row[idx]') on each column specified via the -c flag.

cat 2007.csv | csvgrep -s '(\s+|[a-zA-Z])' -x '\1' -r '.' -c 1 | head

[onyxfish]

I probably won't accept a pull request for this, because I don't believe it makes sense to bring data modification tools into csvkit. It opens up a Pandora's box of "I just want a tool that makes X change to a cell." At a certain point it's just more sensible to use existing tools (code, Excel, whatever). I've resisted this temptation until now and so far haven't regretted it.

[onyxfish]

Rereading, I hope that didn't sound too dismissive. I love that you're hacking on it and if you wanted to make your own repo I'd be happy to link to you from the docs. :)