[Tutor] What is the square brackets about?

[Alan Gauld]

On 16/01/16 22:53, boB Stepp wrote:

>> The function plumbs the depths of thing according to the indices
>> supplies in loc. The shape of thing must match the length of loc.
> 
> The interesting part of this function for me was not the OP's original
> questions, but why this particular use of a recursive function (Am I
> using the proper terminology here?)?  

Yes it's a recursive function.


> Can someone provide a practical
> use of this type of function where some more straightforward
> searching/parsing approach would be ineffective?

In fact its much easier to write this using recursion that
any other method. Its just very difficult to use and so
needs some protection. The difficulty is in getting the
input data structures to match, once that's done the
function itself is very straightforward.

It's a way of quickly navigating a tree structure where the
route to the node (or subtree) of interest is given in
advance. Think of 'loc' as being a directory path broken
into its individual parts and 'thing' as being the file
system represented as a dictionary of dictionaries (for
the named indexing to work). [BTW I haven't tried that to
see if it works it's just a guess at a possible
application...] Of course, for a real filesystem we have
functions in the os module to do the work but that type
of data structure might be the target.

-- 
Alan G
Author of the Learn to Program web site
http://www.alan-g.me.uk/
http://www.amazon.com/author/alan_gauld
Follow my photo-blog on Flickr at:
http://www.flickr.com/photos/alangauldphotos