In C++, if you want your code to talk about itself, you often use the predefined magic macros __FILE__ and __LINE__ to get the filename and line number of the current line:
// Use this macro if you can't write the code yet.
#define NOTYET() NoCodeYet(__FILE__, __LINE__);
void NoCodeYet(const char * pszFile, int nLine)
fprintf(stderr, "No code yet at %s(%d)\n", pszFile, nLine);
NOTYET() // I'll get to this later.
This provides a convenient way to leave breadcrumbs that will direct you to the spot in the code later.
How to do it in Python? With help from the Python Cookbook, I created this. It uses scary functions from sys (_getframe has a leading underscore and is described as "for internal and specialized uses only"):
""" Create a string naming the function n frames up on the stack.
co = sys._getframe(nFramesUp+1).f_code
return "%s (%s @ %d)" % (co.co_name, co.co_filename, co.co_firstlineno)
""" Call this function to indicate that a method isn't implemented yet.
raise Exception("Not yet implemented: %s" % _functionId(1))
This goes one further than the C++ technique, by providing the function name as well as the file and line.