Training, Open Source computer languages

PerlPHPPythonMySQLhttpd / TomcatTclRubyJavaC and C++LinuxCSS

Search our site for:
Home Accessibility Courses Diary The Mouth Forum Resources Site Map About Us Contact
Last elements in a Perl or Python list
How do we refer to the elements of a list? By index number, starting at zero and stopping one short of the number of elements in the list. So a 20 element list has element numbers 0 to 19.

How can we refer to the last element, then? We could write an expression based on the length of the list - so
mylist[len(mylist)-1] in Python
$mylist[@mylist-1] or $mylist[$#mylist] in Perl.
That's going to get very messy if you want to do a lot of work on the end elements of a list, so (in both Perl and Python), you can refer to members of a list by a negative position number, meaning "number of positions from the end".

So:
mylist[-1] - last element of a list in Python
$mylist[-2] - next to last (penultimate) element of a list in Perl
(written 2007-08-16 10:45:30)

 
Associated topics are indexed under
Y111 - Python - More on Collections and Sequences
P208 - Perl - Lists

Back to
Heading Upstate New York
Previous and next
or
Horse's mouth home
Forward to
Regular expressions made easy - building from components

Some other Articles
Good to be home
Troy, up state New York
Python class rattling around
Regular expressions made easy - building from components
Last elements in a Perl or Python list
Heading Upstate New York
Ruby, Ruby, Ruby. Rails, Rails, Rails.
Plastic or China
In the USA for a few days
From Leeds
1638 posts, page by page
Link to page ... 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33 at 50 posts per page


This is a page archived from The Horse's Mouth at http://www.wellho.net/horse/ - the diary and writings of Graham Ellis. Every attempt was made to provide current information at the time the page was written, but things do move forward in our business - new software releases, price changes, new techniques. Please check back via our main site for current courses, prices, versions, etc - any mention of a price in "The Horse's Mouth" cannot be taken as an offer to supply at that price.

Link to Ezine home page (for reading).
Link to Blogging home page (to add comments).

© WELL HOUSE CONSULTANTS LTD., 2008: Well House Manor • 48 Spa Road • Melksham, Wiltshire • United Kingdom • SN12 7NY
PH: 01144 1225 708225 • FAX: 01144 1225 707126 • EMAIL: info@wellho.net • WEB: http://www.wellho.net • SKYPE: wellho