Глобальные переменные до сих пор не распознаны, отзывы о лучших практиках

Question

Кажется, что даже если я объявлю переменные внутри функции global, они все равно не распознаются в программе main ().

Я пытался объявить переменные, которые моя функция scan (string) возвращает как глобальные, чтобы иметь возможность доступа к ним через main (), но интерпретатор по-прежнему жалуется на них с ошибкой .... global_name is "Имя переменной "не определено.

print "\n--------- // Program Lexicon // -------------\n"

direction_words = ('north', 'south', 'east', 'west', 'down', 'up', 'left', 'right', 'back', 'forward')

verbs = ('go', 'stop', 'kill', 'eat', 'run')

nouns = ('door', 'bear', 'princess', 'cabinet')

numbers = ('0', '1', '2', '3', '4', '5', '6', '7', '8', '9')

results_list = []

def scan(string):

    global result_direction, result_verb, result_noun, result_number, result_error

    if string in direction_words:
        print "\nfound match in >> direction words <<: %s" %string
        result_direction = ('direction', string)
        return result_direction

    elif string in verbs:
        print "\nfound match in >> verbs <<: %s" %string
        result_verb = ("verb", string)
        return result_verb

    elif string in nouns:
        print "\nfound match in >> nouns <<: %s" %string
        result_noun = ('noun', string)
        return result_noun

    elif string in numbers:
         print "\nfound match in >> numbers <<: %s" %string
         result_number = ('number', int(string))
         return result_number

    elif string is not verbs or nouns or numbers or directions:
         print "\nmassive error > string < not matching any condition"
         result_error = ('error', string)
         return result_error

    else:
        print "Failure!"


def main():

    user_input = raw_input("\nenter your answer please: ")
    user_words = user_input.split()

    for i in range(len(user_words)):
        look_up_words = user_words[i]
        scan(user_words[i])
        results_list.append(result_direction, result_verb, result_noun, result_number, result_error)


main()


--------- // Program Lexicon // -------------


enter your answer please: south

found match in >> direction words <<: south
Traceback (most recent call last):
  File "lexicon.py", line 60, in <module>
    main()
  File "lexicon.py", line 57, in main
    results_list.append(result_direction, result_verb, result_noun, result_number, result_error)
NameError: global name 'result_verb' is not defined
PS D:\Exersize_46\Python27_Projects\Exersize_48\Exersize_48> python lexicon.py

--------- // Program Lexicon // -------------


enter your answer please: south max east

found match in >> direction words <<: south
Traceback (most recent call last):
  File "lexicon.py", line 60, in <module>
    main()
  File "lexicon.py", line 57, in main
    results_list.append(result_direction, result_noun, result_number, result_error)
NameError: global name 'result_noun' is not defined
PS D:\Exersize_46\Python27_Projects\Exersize_48\Exersize_48>