settrace(tracefunc)

Set the system's trace function, which allows you to implement a Python source code debugger in Python. See the section How It Works, in the chapter on the Python debugger. The function is thread-specific; for a debugger to support multiple threads, it must be registered using sys.settrace for each thread being debugged. Note: The sys.settrace function is intended only for implementing debuggers, profilers, coverage tools and the like. Its behavior is part of the implementation platform, rather than part of the language definition, and thus may not be available in all Python implementations.