Pandas ENH: Add prefix parameters for join method.

It would be nice if the join method had lprefix and rprefix parameters in analogy to lsuffix and rsuffix. P.S. No pull request, sorry.

Comment From: jorisvandenbossche

@onesandzeroes (answering here) I am not really sure about this one in terms of adding clutter to the api. 4 keywords seems a lot for this.

BTW, if we add this, we should certainly first look at consistency within the API of similar functions. Eg pd.merge has a suffixes keyword that accepts a tuple (for left, right) instead of two seperate keyword.

Comment From: TomAugspurger

Unlikely to be implemented I think.