Built-in String Functions

Strings have methods that you can call on them. However, there are also built-in functions that are relevant to strings. A few that we'll use include:

len(s) - the length of a string
ord(s) - the code point of the character supplied
chr(i) - the character represented by the supplied code point

The Built-In len() Function

len is a built-in function that returns the length of a sequence

it is not a method, so you do not call it on an object
however, you can pass a value to it, and it will return its length
for strings, it will return the number of characters

s = "cat"

#  returns 3
print(len(s))

Index of the Last Character in a String

What's the formula for getting the last character in a string? →

length of string - 1

Index of the Last Character in a String Continued

What values / expressions would you use if you wanted to index into the string below to get the last character? →

s = "cat"
print(s[?])

print(s[2])
print(s[-1])
print(s[len(s) - 1])

Representing Strings

There's a standard for consistently representing text through different character sets and encodings.

this system is called unicode
in unicode, code points are numbers (specifically integers) that represents a character or glyph
here's a table of code points
here's a unicode snowman

Unicode Table

Let's see that table again.

note that 65-90 are uppercase latin letters; 97-122 are lowercase
this matches an older method of encoding characters called ASCII
- ASCII accomodated 128 characters
- what are some shortcomings of this? →

chr() and ord()

Python has a couple of functions that translate code points to characters and characters back to code points.

ord(c) - gives back the integer value of the code point of the supplied character
chr(i) - gives back the character corresponding to the supplied integer (code point)