Found on http://stackoverflow.com/questions/24165374/printing-a-functions-local-variable-names-and-values

1-Tested.md

I wanted to get a way to inspect the value of variables when a function was called without modifying the code. I tested it on a simple function, and it does what I wanted.

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date: '2014-07-11T23:59:00+07:00'
doc: <Element {http://www.w3.org/1999/xhtml}html at 0x10c180638>
DATETYPE: 'created'
finddate: string(//__xpp1:time[@class='created']/@datetime)
Returned: '2014-07-11T23:59:00+07:00'
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--------------------------------------------------------------------------------
date: '2014-09-08T18:21:00+09:00'
doc: <Element {http://www.w3.org/1999/xhtml}html at 0x10c180638>
DATETYPE: 'modified'
finddate: string(//__xpp1:time[@class='modified']/@datetime)
Returned: '2014-09-08T18:21:00+09:00'
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2-show_guts.py

import sys
import threading

def show_guts(f):
    sentinel = object()
    gutsdata = threading.local()
    gutsdata.captured_locals = None
    gutsdata.tracing = False

    def trace_locals(frame, event, arg):
        if event.startswith('c_'):  # C code traces, no new hook
            return
        if event == 'call':  # start tracing only the first call
            if gutsdata.tracing:
                return None
            gutsdata.tracing = True
            return trace_locals
        if event == 'line':  # continue tracing
            return trace_locals

        # event is either exception or return, capture locals, end tracing
        gutsdata.captured_locals = frame.f_locals.copy()
        return None

    def wrapper(*args, **kw):
        # preserve existing tracer, start our trace
        old_trace = sys.gettrace()
        sys.settrace(trace_locals)

        retval = sentinel
        try:
            retval = f(*args, **kw)
        finally:
            # reinstate existing tracer, report, clean up
            sys.settrace(old_trace)
            print '-' * 80
            for key, val in gutsdata.captured_locals.items():
                print '{}: {!r}'.format(key, val)
            if retval is not sentinel:
                print 'Returned: {!r}'.format(retval)
            print '-' * 80
            gutsdata.captured_locals = None
            gutsdata.tracing = False

        return retval
    return wrapper

3-Tested-function.py

@show_guts
def getdocdate(doc, DATETYPE):
    '''return the creation date of the document in ISO format YYYY-MM-DD
    Input the document, typeofdate in between created and modified
    '''
    if DATETYPE not in DATETYPELIST:
        sys.exit("ERROR: No valid type for the date: " + DATETYPE)
    finddate = etree.ETXPath(
        "string(//{%s}time[@class=%r]/@datetime)" % (HTMLNS, DATETYPE))
    date = finddate(doc)
    return date