Slicing

A slice is a subset of a string or other element. A slice could be the whole element or one character, but it's more commonly a group of adjoining characters.

Let's say you want to access the fifth through eleventh letters of a string. So, you start at index 4 and end at index 10, as was explained in the previous Indexing section. When slicing, the colon symbol (:) is inserted between indices, like so: [4:10].

There is one caveat. The lower bound of a slice is always included, but the upper bound is not. So, in the preceding example, if you want to include the 10th index, you must use [4:11].

You should now have a look at the following example for slicing.

Retrieve the fifth through eleventh letters of San Francisco, which you used in the previous Indexing section:

destination[4:11]

You should get the following output:

'Francis'

Retrieve the first three letters of destination:

destination[0:3]

You should get the following output:

'San'

There is a shortcut for getting the first n letters of a string. If the first numerical character is omitted, Python will start at the 0th index.

Now, to retrieve the first eight letters of destination using the shortcut, use the following code:

destination[:8]

You should get the following output:

'San Fran'

Finally, to retrieve the last three letters of destination, use this code:

destination[-3:]

You should get the following output:

'sco'

The negative sign, -, means that we start at the third-to-last letter, and the colon means that we go to the end.

Strings and Their Methods

You started with string syntax, before moving on to a variety of ways to concatenate strings. You looked at useful built-in functions including len() and examined a sample of string methods. Next, you casted numbers as strings and vice versa.

The input() function is used to access user input. This really extends what you can do. Responding to user feedback is a core element of programming that you will continue to develop. Finally, you closed with two powerful tools that developers frequently use: indexing and slicing.

There is a great deal more to learn about strings. You will encounter additional problems and methods throughout this book. This introductory chapter is meant to equip you with the basic skills needed to handle strings going forward.

Next, you will learn how to branch programs using conditionals and Booleans.