foo.py

   def print_grid(columns, values):
    # pop columns on top of values, since we want to print them as well
    values = [columns] + values

    # calculate the format string for printing a row
    row_format = ''
    for index in range(len(columns)):
        longest = max([len(str(row[index])) for row in values])
        row_format += '{:' + str(longest) + '} '

    # print the row!
    for row in values:
        print row_format.format(*row)
   
    print_grid(('Function', 'Occurences', 'Sender'), [(x['function'], x['sender']) for x in messages if 'function' in x])
    print '\n\n\n'
    #print '{0: <30}{1: <15}{2:}'.format('Function', 'Occurrence', 'Sender')
    # this prints out all the signal names, and their respective occurences
    grouped = itertools.groupby(sorted(function_messages, key=groupby_key), groupby_key)
    for group, items in grouped:
        items = list(items)
        print '{func:<30}{occurences:<15}{path}'.format(
            func=items[0]['function'],
            occurences=len(items),
            path=items[0]['path']
        )