18.6. Hand-Coded Parsers

Since Python is a general purpose programming language, it's also reasonable to consider writing a hand-coded parser. For instance, recursive descent parsing is a fairly well-known technique for analyzing language-based information. Since Python is a very high-level language, writing the parser itself is usually easier than it would be in a traditional language like C or C++.

To illustrate, this section develops a custom parser for a simple grammar: it parses and evaluates arithmetic expression strings. This example also demonstrates the utility of Python as a general-purpose programming language. Although Python is often used as a frontend or rapid development language, it's also useful for the kinds of things we'd normally write in a systems development language like C or C++.