8.1 Variables with more than one value

You have already seen ordinary variables that store a single value. However other variable types can hold more than one value. The simplest type is called a list. Here is a example of a list being used:

which_one = input("What month (1-12)? ")
months = ['January', 'February', 'March', 'April', 'May', 'June', 'July',\
	'August', 'September', 'October', 'November', 'December']
if 1 <= which_one <= 12:
        print "The month is",months[which_one - 1]

and a output example:

What month (1-12)? 3
The month is March

In this example the months is a list. months is defined with the lines months = ['January', 'February', 'March', 'April', 'May', 'June', 'July',\ 'August', 'September', 'October', 'November', 'December'] (Note that a \ can be used to split a long line). The [ and ] start and end the list with comma's (``,'') separating the list items. The list is used in months[which_one - 1]. A list consists of items that are numbered starting at 0. In other words if you wanted January you would use months[0]. Give a list a number and it will return the value that is stored at that location.

The statement if 1 <= which_one <= 12: will only be true if which_one is between one and twelve inclusive (in other words it is what you would expect if you have seen that in algebra).

Lists can be thought of as a series of boxes. For example, the boxes created by demolist = ['life',42, 'the universe', 6,'and',7] would look like this:

box number 0 1 2 3 4 5
demolist `life' 42 `the universe' 6 `and' 7

Each box is referenced by its number so the statement demolist[0] would get 'life', demolist[1] would get 42 and so on up to demolist[5] getting 7.