Page 42 - Programming the Raspberry Pi Getting Started with Python

You can chop lumps out of a big string into a smaller string, like this:

The first number within the brackets is the starting position for the string we want to chop out, and
the second number is not, as you might expect, the position of the last character you want, but rather

the last character plus 1.
As an experiment, try and chop out the word raspberry from the title. If you do not specify the
second number, it will default to the end of the string:

Similarly, if you do not specify the first number, it defaults to 0.
Finally, you can also join strings together by using + operator. Here’s an example:

Lists

Earlier in the book when you were experimenting with numbers, a variable could only hold a single
number. Sometimes, however, it is useful for a variable to hold a list of numbers or strings, or a
mixture of both—or even a list of lists. Figure 4-1 will help you to visualize what is going on when a
variable is a list.

Figure 4-1 An array
Lists behave rather like strings. After all, a string is a list of characters. The following example
shows you how to make a list. Notice how len works on lists as well as strings:

Square brackets are used to indicate a list, and just like with strings we can use square brackets to

find an individual element of a list or to make a shorter list from a bigger one:

What’s more, you can use = to assign a new value to one of the items in the list, like this:

This changes the first element of the list (element 0) from 123 to just 1.
As with strings, you can join lists together using the + operator: