Python in a Nutshell

Chapter 9. Strings and Regular Expressions

Python supports plain and Unicode strings extensively, with statements, operators, built-in functions, methods, and dedicated modules. This chapter covers the methods of string objects, talks about string formatting, documents the string, pprint, and repr modules, and discusses issues related to Unicode strings.

Regular expressions let you specify pattern strings and allow searches and substitutions. Regular expressions are not easy to master, but they are a powerful tool for processing text. Python offers rich regular expression functionality through the built-in re module, as documented in this chapter.

Methods of String Objects

Plain and Unicode strings are immutable sequences, as covered in Chapter 4. All immutable-sequence operations (repetition, concatenation, indexing, slicing) apply to strings. A string object s also supplies several non-mutating methods, as documented in this section. Unless otherwise noted, each method returns a plain string when s is a plain string, or a Unicode string when s is a Unicode string. Terms such as letters, whitespace, and so on refer to the corresponding attributes of the string module, covered later in this chapter. See also the later section Section 9.2.1.