Python Cookbook

Determining the Name of the Current Function

Credit: Alex Martelli

Problem

You have error messages that include the name of the function emitting them. To copy such messages to other functions, you have to edit them each time, unless you can automatically find the name of the current function.

Solution

This introspective task is easily performed with sys._getframe. This function returns a frame object whose attribute f_code is a code object and the co_name attribute of that object is the function name:

import sys
this_function_name = sys._getframe(  ).f_code.co_name

The frame and code objects also offer other useful information:

this_line_number = sys._getframe(  ).f_lineno
this_filename = sys._getframe(  ).f_code.co_filename

By calling sys._getframe(1), you can get this information for the caller of the current function. So you can package this functionality into your own handy functions:

def whoami(  ):
    import sys
    return sys._getframe(1).f_code.co_name

me  = whoami(  )

This calls sys._getframe with argument 1, because the call to whoami is now frame 0. Similarly:

def callersname(  ):
    import sys
    return sys._getframe(2).f_code.co_name

him = callersname(  )

Discussion

You want to determine the name of the currently running function—for example, to create error messages that don’t need to be changed when copied to other functions. The function _getframe function of the sys module does this and much more. This recipe is inspired by Recipe 10.4 in the Perl Cookbook. Python’s sys._getframe, new in 2.1, offers information equivalent to (but richer than) Perl’s built-in caller, _ _LINE_ _, and _ _FILE_ _. If you need this functionality for older Python releases, see Recipe 14.9.

See Also

Recipe 14.9 for a version that works with older Python versions; documentation on the _getframe method of the sys module in the Library Reference; Perl Cookbook Recipe 10.4.