Learning Python

Strings

The next major built-in type is the Python string —an ordered collection of characters, used to store and represent text-based information. From a functional perspective, strings can be used to represent just about anything that can be encoded as text: symbols and words (e.g., your name), contents of text files loaded into memory, and so on.

You’ve probably used strings in other languages too; Python’s strings serve the same role as character arrays in languages such as C, but Python’s strings are a higher level tool. Unlike C, there is no char type in Python, only one-character strings. And strictly speaking, Python strings are categorized as immutable sequences— big words that just mean that they respond to common sequence operations but can’t be changed in place. In fact, strings are representative of the larger class of objects called sequences; we’ll have more to say about what this means in a moment, but pay attention to the operations introduced here, because they’ll work the same on types we’ll see later.

Table 2.4 introduces common string constants and operations. Strings support expression operations such as concatenation (combining strings), slicing (extracting sections), indexing (fetching by offset), and so on. Python also provides a set of utility modules for processing strings you import. For instance, the string module exports most of the standard C library’s string handling tools, and the regex and re modules add regular expression matching for strings ...