Python in a Nutshell

Debugging

Since Python’s development cycle is so fast, the most effective way to debug is often to edit your code to make it output relevant information at key points. Python has many ways to let your code explore its own state in order to extract information that may be relevant for debugging. The inspect and traceback modules specifically support such exploration, which is also known as reflection or introspection.

Once you have obtained debugging-relevant information, statement print is often the simplest way to display it. You can also log debugging information to files. Logging is particularly useful for programs that run unattended for a long time, as is typically the case for server programs. Displaying debugging information is like displaying other kinds of information, as covered in Chapter 10 and Chapter 16, and similarly for logging it, as covered in Chapter 10 and Chapter 11. Python 2.3 will also include a module specifically dedicated to logging. As covered in Chapter 8, rebinding attribute excepthook of module sys lets your program log detailed error information just before your program is terminated by a propagating exception.

Python also offers hooks enabling interactive debugging. Module pdb supplies a simple text-mode interactive debugger. Other interactive debuggers for Python are part of integrated development environments (IDEs), such as IDLE and various commercial offerings. However, I do not cover IDEs in this book.

The inspect Module

The inspect module supplies ...