The Unicode standard provides an entire database—in the form of several structured text files—that includes not only the table mapping code points to character names, but also metadata about the individual characters and how they are related. For example, the Unicode database records whether a character is printable, is a letter, is a decimal digit, or is some other numeric symbol. That’s how the str methods isalpha, isprintable, isdecimal, and isnumeric work. str.casefold also uses information from a Unicode table.
