Exactly. l1=[1,2,3] l2=[4,5,6] l1.append(l2) len(l1) 4 But now, if we instead do: l1.extend(l2) len(l1) 6 On 12/8/10, Homme, James <james.homme@xxxxxxxxxxxx> wrote: > Hi Alex, > So it sounds like if you say len(l1) after the first example, the result > will be 2, since there are two lists. And len(l1) after the extend example > will give you a list length that includes all of the elements. I didn't > count them. > > Thanks. > > Jim > > > > Jim Homme, > Usability Services, > Phone: 412-544-1810. Skype: jim.homme > Internal recipients, Read my accessibility blog. Discuss accessibility > here. Accessibility Wiki: Breaking news and accessibility advice > > > -----Original Message----- > From: programmingblind-bounce@xxxxxxxxxxxxx > [mailto:programmingblind-bounce@xxxxxxxxxxxxx] On Behalf Of Alex Hall > Sent: Wednesday, December 08, 2010 10:50 AM > To: programmingblind@xxxxxxxxxxxxx > Subject: Re: Python: Question About Extend And Append Built-in Functions > > The append method will ad the object as its own element, so appending > a list to a list will give you a 2d list (or at least will give you a > list as one element of your parent list). > Extend, on the other hand, will add the elements of the list to the > list being extended. This means that, insteading of the entire list > being added as one element, all elements are appended one at a time. > For example: > > l1=[1,2] > l2=[3,4] > l1.append(l2) > will give us a list with elements 1, 2, and [3,4]. This means that > l1[2] will be the entire list [3,4], not just 3, and l1[3] will throw > an exception. > > However, l1.extend(l2) will give us a list 1, 2, 3, 4, so l1[2]=3 and > l1[3]=4 and is now valid. I hope this makes sense. > > On 12/8/10, Homme, James <james.homme@xxxxxxxxxxxx> wrote: >> Hi, >> One of the most frustrating things in life is to try to read programming >> documentation written by programmers. It's not clear at all, so here goes >> my >> questioning. >> >> Are they trying to say that the difference between append and extend is >> basically that you can only append one of something to the end of the list >> and that when you use extend that you can append multiple things? And a >> related question is: when you use extend, are you allowed to put any kind >> of >> thing you want onto the end of a list? For example, if you have a list of >> strings, can you use extend to put a string and a list of strings onto the >> end of your list? I don't know why you'd do that, but I'm just asking if >> you >> can. >> >> Thanks. >> >> Jim >> Jim Homme, >> Usability Services, >> Phone: 412-544-1810. Skype: jim.homme >> Internal recipients, Read my accessibility >> blog<http://mysites.highmark.com/personal/lidikki/Blog/default.aspx>. >> Discuss accessibility >> here<http://collaborate.highmark.com/COP/technical/accessibility/default.aspx>. >> Accessibility Wiki: Breaking news and accessibility >> advice<http://collaborate.highmark.com/COP/technical/accessibility/Accessibility%20Wiki/Forms/AllPages.aspx> >> >> >> ________________________________ >> This e-mail and any attachments to it are confidential and are intended >> solely for use of the individual or entity to whom they are addressed. If >> you have received this e-mail in error, please notify the sender >> immediately >> and then delete it. If you are not the intended recipient, you must not >> keep, use, disclose, copy or distribute this e-mail without the author's >> prior permission. The views expressed in this e-mail message do not >> necessarily represent the views of Highmark Inc., its subsidiaries, or >> affiliates. >> > > > -- > Have a great day, > Alex (msg sent from GMail website) > mehgcap@xxxxxxxxx; http://www.facebook.com/mehgcap > __________ > View the list's information and change your settings at > //www.freelists.org/list/programmingblind > > __________ > View the list's information and change your settings at > //www.freelists.org/list/programmingblind > > -- Have a great day, Alex (msg sent from GMail website) mehgcap@xxxxxxxxx; http://www.facebook.com/mehgcap __________ View the list's information and change your settings at //www.freelists.org/list/programmingblind