Super Verbose python debugging

import sys

def traceit(frame, event, arg):
    """
    used by sys.settrace() to provide trace dumps for python apps
    this function returns itself, per expectation of sys.settrace()
    from Andrew Dalke's blog at http://www.dalkescientific.com/writings/diary/archive/2005/04/20/tracing_python_code.html
 
    This env var TDNUKE_TRACE_DEBUG can take on the values defined in
    http://docs.python.org/lib/debugger-hooks.html, ie: 
    'call', 'line', 'return', 'exception', 'c_call', 'c_return' and 'c_exception'. 
    Empty string equivalent to 'call'. 
    setenv TDNUKE_TRACE_DEBUG call
    setenv TDNUKE_TRACE_DEBUG line
    setenv TDNUKE_TRACE_DEBUG return
    setenv TDNUKE_TRACE_DEBUG exception
    setenv TDNUKE_TRACE_DEBUG c_call
    setenv TDNUKE_TRACE_DEBUG c_return
    setenv TDNUKE_TRACE_DEBUG c_exception
    unsetenv TDNUKE_TRACE_DEBUG  to stop printing
    """
    if event == os.environ['TDNUKE_TRACE_DEBUG']:
        lineno = frame.f_lineno
        filename = ''
        if frame.f_globals.has_key("__file__"):
            filename = frame.f_globals["__file__"]
        if (filename.endswith(".pyc") or
            filename.endswith(".pyo")):
            filename = filename[:-1]
        name = frame.f_globals["__name__"]
        line = linecache.getline(filename, lineno)
        if 'nuke' in name.lower():
            sys.stderr.write("%s:%s: %s\n" % (name, lineno, line.rstrip()))
    sys.stderr.flush()
    return traceit
 
 
if os.environ.has_key('TDNUKE_TRACE_DEBUG'):
    import linecache
    if os.environ['TDNUKE_TRACE_DEBUG'] == '':
        os.environ['TDNUKE_TRACE_DEBUG'] = 'call' # returns function called
    sys.settrace(traceit)