Regular Expressions

Abstract

Every modern programming language has built-in functions for working with strings. In Python, strings have methods for searching and replacing: index(), find(), split(), count(), replace(), and so on. But these methods are limited to the simplest of cases. For example, the index() method looks for a single, hard-coded substring, and the search is always case-sensitive. To do case-insensitive searches of a string s, you must call s.lower() or s.upper() and make sure that your search strings are the appropriate case to match. The replace() and split() methods have the same limitations.