diff -r e78c284d644b -r 223044cf254f getting-started-with-lists/getting_started_with_lists.rst --- /dev/null Thu Jan 01 00:00:00 1970 +0000 +++ b/getting-started-with-lists/getting_started_with_lists.rst Wed Oct 13 17:10:38 2010 +0530 @@ -0,0 +1,137 @@ +Hello friends and welcome to the tutorial on getting started with +lists. + + {{{ Show the slide containing title }}} + + {{{ Show the slide containing the outline slide }}} + +In this tutorial we will be getting acquainted with a python data +structure called lists. We will learn :: + + * How to create lists + * Structure of lists + * Access list elements + * Append elements to lists + * Deleting elements from lists + +List is a compound data type, it can contain data of other data +types. List is also a sequence data type, all the elements are in +order and there order has a meaning. + +We will first create an empty list with no elements. On your IPython +shell type :: + + empty = [] + type(empty) + + +This is an empty list without any elements. + +* Filled lists + +Lets now define a list, nonempty and fill it with some random elements. + +nonempty = ['spam', 'eggs', 100, 1.234] + +Thus the simplest way of creating a list is typing out a sequence +of comma-separated values (items) between square brackets. +All the list items need not have the same data type. + + + +As we can see lists can contain different kinds of data. In the +previous example 'spam' and 'eggs' are strings and 100 and 1.234 +integer and float. Thus we can put elements of heterogenous types in +lists. Thus list themselves can be one of the element types possible +in lists. Thus lists can also contain other lists. Example :: + + list_in_list=[[4,2,3,4],'and', 1, 2, 3, 4] + +We access list elements using the number of index. The +index begins from 0. So for list nonempty, nonempty[0] gives the +first element, nonempty[1] the second element and so on and +nonempty[3] the last element. :: + + nonempty[0] + nonempty[1] + nonempty[3] + +We can also access the elememts from the end using negative indices :: + + nonempty[-1] + nonempty[-2] + nonempty[-4] + +-1 gives the last element which is the 4th element , -2 second to last and -4 gives the fourth +from last element which is first element. + +We can append elements to the end of a list using append command. :: + + nonempty.append('onemore') + nonempty + nonempty.append(6) + nonempty + +As we can see non empty appends 'onemore' and 6 at the end. + + + +Using len function we can check the number of elements in the list +nonempty. In this case it being 6 :: + + len(nonempty) + + + +Just like we can append elements to a list we can also remove them. +There are two ways of doing it. One is by using index. :: + + del(nonempty[1]) + + + +deletes the element at index 1, i.e the second element of the +list, 'eggs'. The other way is removing element by content. Lets say +one wishes to delete 100 from nonempty list the syntax of the command +should be :: + + a.remove(100) + +but what if their were two 100's. To check that lets do a small +experiment. :: + + a.append('spam') + a + a.remove('spam') + a + +If we check a now we will see that the first occurence 'spam' is removed +thus remove removes the first occurence of the element in the sequence +and leaves others untouched. + + +{{{Slide for Summary }}} + + +In this tutorial we came across a sequence data type called lists. :: + + * We learned how to create lists. + * How to access lists. + * Append elements to list. + * Delete Element from list. + * And Checking list length. + + + +{{{ Sponsored by Fossee Slide }}} + +This tutorial was created as a part of FOSSEE project. + +I hope you found this tutorial useful. + +Thank You + + + * Author : Amit Sethi + * First Reviewer : + * Second Reviewer : Nishanth