'dict_keys' 对象不支持索引

Question

我正在使用 Learn Python the Hard Way 来学习 Python，当我运行以下作为示例提供的代码时，我遇到了 'dict_keys' object does not support indexing error：

import random
from urllib.request 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 *** function, and call it with parameters self, @@@.",
    "***.*** = '***'":
      "From *** get the *** attribute and set it to '***'."
}

# do they want to drill phrases first
if len(sys.argv) == 2 and sys.argv[1] == "english":
    PHRASE_FIRST = True
else:
    PHRASE_FIRST = False

# 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


# keep going until they hit CTRL-D
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 = list(answer)
                answer = list(question)

            print(question)

            input("> ")
            print("ANSWER:  %s\n\n" % answer)
except EOFError:
    print("\nBye")

此代码适用于 Python 2.x，而我使用的是 Python 3.5。我看到了以下帖子，但无法将解决方案转换为上述帖子：TypeError: 'dict_keys' object does not support indexing。任何帮助表示赞赏。

Answer 1

尝试替换这个

snippets = PHRASES.keys()

有了这个

snippets = list(PHRASES.keys())

正如您提供的链接中所说，dict.keys() 不会在 python 3 中返回列表。

Answer 2

因此，您需要注意 Python 2.X 和 Python 3.5.x 之间存在一些差异。

来自@jprokbelly 的答案将帮助您实现目标，但您还需要修改convert 函数中的代码，因为来自urllib.request 的urlopen 将返回字节流而不是字符串，这将导致错误消息：

TypeError: Can't convert 'bytes' object to str implicitly

因此，如果您想将此代码用于 Python 3.5.x，那么您至少需要做两件事。

1. 将snippets = PHRASES.keys() 更改为snippets = list(PHRASES.keys()]

2. 将convert方法的开头改为：

   def convert(snippet, phrase):
       class_names = [w.capitalize() for w in random.sample(WORDS, snippet.count("%%%"))]
       other_names = random.sample(WORDS, snippet.count("***"))
       class_names = [name.decode('UTF-8') for name in class_names]
       other_names = [name.decode('UTF-8') for name in other_names]
   

您的另一个选择是将您的开发环境设置为使用 virtualenv 并在 Python 2.7.x 中运行代码。

Answer 3

这里有两个问题（在其他答案中提到），因为 Python 2 和 3 中对字符串/字节类型的不同处理（影响 3 行代码）和对象索引（影响 1 行）。以下运行调整完成后（4行代码）就ok了：

import random
from urllib.request 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 *** function, and call it with parameters self, @@@.",
    "***.*** = '***'":
      "From *** get the *** attribute and set it to '***'."
}

# do they want to drill phrases first
if len(sys.argv) == 2 and sys.argv[1] == "english":
    PHRASE_FIRST = True
else:
    PHRASE_FIRST = False

# 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(str(WORDS), param_count)))

    for sentence in snippet, phrase:
        result = sentence[:]
        # print(type(result))

        # fake class names
        for word in class_names:
            # print(type(word))
            result = result.replace("%%%", word.decode("utf-8"), 1)

        # fake other names
        for word in other_names:
            result = result.replace("***", word.decode("utf-8"), 1)

        # fake parameter lists
        for word in param_names:
            result = result.replace("@@@", word.decode("utf-8"), 1)

        results.append(result)

    return results


# keep going until they hit CTRL-D
try:
    while True:
        for i, item in enumerate(PHRASES.keys()): 
          print(i, "###", item)

        snippets = list(PHRASES.keys())
        random.shuffle(snippets)

        for snippet in snippets:
            phrase = PHRASES[snippet]
            question, answer = convert(snippet, phrase)
            if PHRASE_FIRST:
                question = list(answer)
                answer = list(question)

            print(question)

            input("> ")
            print("ANSWER:  %s\n\n" % answer)
except EOFError:
    print("\nBye")