There are exceptions, but not as many as you might think if you are used to other languages. The re module obsoletes the regex and regsub modules that you may see used in some older Python code. While there are still a few, limited advantages to regex , they are minor and it is not worth using in new code. The obsolete modules are likely to be dropped from future Python releases, and 1.6 will probably have an improved interface-compatible re module. So stick with re for regular expressions.
Regular expressions are complicated.
A regular expression is a concise way of describing a pattern that might occur in a text. Conceptually, this is not unlike the way you would intuitively describe a pattern in a natural language. The trick is encoding this description in the compact syntax of regular expressions. Start with the smallest pieces. The simplest character class is a single character, which is just included in the pattern as a literal.