In Chapter 4¹, strings were quickly introduced. The brief discussion in that chapter ended with the statement that a string is a text, enclosed by either single or double quotes, which might be of any length, including zero characters long. The chapter also explained that you can concatenate two strings using the +, and that you can create a string that is the repetition of a shorter string by using a *. For example:

s1 = "apple"
s2 = 'banana'
print( s1 )
print( s2 )
print( s1 + s2 )
print( 3 * s1 )
print( s2 * 3 )
print( 2 * s1 + 2 * s2 )

Chapter 6² introduced the format() function to format strings. It also explained how you can get the length of a string using the len() function.

String comparisons were explained in Chapter 7³, in particular the fact that the comparison operators compare strings using alphabetical rules, whereby capitals are always lower in the alphabet than lower case letters. This will be explained more in-depth in the present chapter. Chapter 7⁴ also explained how the in operator can be used to test the presence of characters or substrings in strings.

Chapter 8⁵ explained how you can use a for loop to traverse all the characters in a string.

s1 = "orange"
s2 = "banana"
for letter in s1:
    if letter in s2:
        print( s1, "and", s2, "share the letter", letter )