ValueError: 需要超过1个值进行解包：学习Python的艰难方式示例41

Question

我正在尝试让《Learn Python The Hard Way》里的一个脚本正常运行。最开始有6个错误，我把它减少到只剩下一个错误。但是这个错误我试了好几个小时还是解决不了。这个错误信息是：

E:\PythonCode>python oop_test.py 回溯（最近的调用在最前面）： 文件 "oop_test.py"，第72行，在 question, answer = convert(snippet,phrase)[0] 值错误：要解包的值太多了

以下是完整的源代码：

import random
from urllib import urlopen
import sys

WORD_URL = "http://learncodethehardway.org/words.txt"

WORDS = []

PHRASES = {
    "class %%%(%%%): ":
    "Make a class named %%% that is-a %%%",
    "class %%%(object):\n\tdef __init__(self, ***)":
    "class %%% has-a __init__ that takes self and *** parameters",
    "class %%%(object):\n\tdef ***(self, @@@)":
    "class %%% has-a function named *** that takes self and @@@ parameters.",
    "*** = %%%()":
    "Set *** to an instance of class %%%.",
    "***.***(@@@)":
    "From *** get the *** attribute and set it to '***'."
}

#do they want to drill phrases first

PHRASE_FIRST = False

if len(sys.argv) == 2 and sys.argv[1] == "english":
    PHRASE_FIRST = True

#load up the words from the website

for word in urlopen(WORD_URL).readlines():
    WORDS.append(word.strip())

def convert(snippet, phrase):
     class_names = [w.capitalize() for w in random.sample(WORDS, snippet.count("%%%"))]

     other_names = random.sample(WORDS, snippet.count("***"))

     results = []
     param_names = []

     for i in range(0, snippet.count("@@@")):
        param_count = random.randint(1,3)
        param_names.append(','.join(random.sample(WORDS, param_count)))

     for sentence in snippet, phrase:
         result = sentence[:]

     #fake class names
     for word in class_names:
        result = result.replace("%%%", word, 1)

     #fake other names
     for word in other_names:
        result  = result.replace("***", word, 1)

     #fake parameter lists
     for word in param_names:
        result = result.replace("@@@", word, 1)

     results.append(result)
     return results


try :
    while True : 
        snippets = PHRASES.keys()
        random.shuffle(snippets)

        for snippet in snippets:
            phrase = PHRASES[snippet]
            question, answer = convert(snippet,phrase)
            if PHRASE_FIRST:
                question, answer = answer, question
            print question
            raw_input("> ")
            print "ANSWER: %s\n\n" % answer
except EOFError:
    print "\nBye"   

Answer 1

在第39行，你说：

results = []

经过几次操作后，在第61行，你终于：

results.append(result)
return results

所以，results 里只能有一个成员。但是在第72行（你的错误），你写了：

question, answer = convert(snippet,phrase)

你不能从一个只包含一个元素的列表中提取两个项目，正如@AdamSmith在评论中正确指出的那样。 :)