Shiyuan [2014-08-24 11:27:32 -07:00] wrote:

> Anyone can explain what is the meaning of the symbol # in the
> following mapconcat call (from ob-python.el),

It's part of read syntax #' which is short-hand for special form
(function ...). That is, both of the following are the same:

    (function foo)
    #'foo

They return the function object of symbol foo.

http://www.gnu.org/software/emacs/manual/html_node/elisp/Anonymous-Functions.html