Strings
Python strings are what we call
objects
, meaning that they have both state
and
behavior. In contrast, data types like
int
,
float
, and
bool
only have a single value.
When we say that strings have state and behavior, we are referring to two important properties of strings:
state–strings are a certain sequence of characters in a certain order. We can think of this as the value of the string.
behavior–strings can do things, like tell us whether or not they are uppercase or count the number of times a certain character occurs in them.
In this section, we’ll look at how to put special characters in strings and accessing specific characters in a string (for instance, the 3rd character). These are all topics associated with the state of a string.
To learn more about string behavior, see the
section on using string functions
.
Escaping Characters in Strings
Also known as: including special characters in strings.
Some characters won’t work for us to just type into a string. For instance, what if our string includes quotation marks? What if our string spans multiple lines? What if our string needs to include a tab character?
To put these characters into strings, we will need to
escape
them. This means that we will write them in a special format so that python knows what we want in the string while still being able to type it as a regular string. Our escape character is the backslash
\
. We will type the backslash before the character that we’d like to escape. For instance, to print
"
, we’ll type
"\""
.
Say we’d like to print the string:
they said "hello"
.
# one strategy is to use single quotes around the string
print('they said "hello"')
String Indexing
String indexing is how we talk about accessing a specific character in a string. Since strings are made of a sequence of characters in a specific order, we’d like to be able to access the 1st, 2nd, 3rd, etc character of the string.
Let’s take a look at the following string:
This string has 8 characters that go from index 0 to index 7.
To access a character at a given index, we use the syntax string_variable[index_number].
Take a look at the following code:
# TODO: run this code.
# Play around with the integer value between the square brackets
s = "dinosaur"
print(s[0])
# TODO: run this code.
# What happens if we give an index value for an index that doesn't
# exist in the string?
# Answer:
s = "dinosaur"
print(s[8])
