从另一个类运行 Python 方法时出现异常

Question

这是我的代码。

import urllib2
import urllib
import json
from BeautifulSoup import BeautifulSoup

class parser:
    """
    This class uses the Beautiful Soup library to scrape the information from
    the HTML source code from Google Translate.

    It also offers a way to consume the AJAX result of the translation, however
    encoding on Windows won't work well right now so it's recommended to use
    the scraping method.
    """

    def fromHtml(self, text, languageFrom, languageTo):
        """
        Returns translated text that is scraped from Google Translate's HTML
        source code.
        """
        langCode={
            "arabic":"ar", "bulgarian":"bg", "chinese":"zh-CN",
            "croatian":"hr", "czech":"cs", "danish":"da", "dutch":"nl",
            "english":"en", "finnish":"fi", "french":"fr", "german":"de",
            "greek":"el", "hindi":"hi", "italian":"it", "japanese":"ja",
            "korean":"ko", "norwegian":"no", "polish":"pl", "portugese":"pt",
            "romanian":"ro", "russian":"ru", "spanish":"es", "swedish":"sv" }

        urllib.FancyURLopener.version = "Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.0.1) Gecko/2008070400 SUSE/3.0.1-0.1 Firefox/3.0.1"

        try:
            postParameters = urllib.urlencode({"langpair":"%s|%s" %(langCode[languageFrom.lower()],langCode[languageTo.lower()]), "text":text,"ie":"UTF8", "oe":"UTF8"})
        except KeyError, error:
            print "Currently we do not support %s" %(error.args[0])
            return

        page = urllib.urlopen("http://translate.google.com/translate_t", postParameters)
        content = page.read()
        page.close()

        htmlSource = BeautifulSoup(content)
        translation = htmlSource.find('span', title=text )
        return translation.renderContents()


    def fromAjaxService(self, text, languageFrom, languageTo):
        """
        Returns a simple string translating the text from "languageFrom" to
        "LanguageTo" using Google Translate AJAX Service.
        """
        LANG={
            "arabic":"ar", "bulgarian":"bg", "chinese":"zh-CN",
            "croatian":"hr", "czech":"cs", "danish":"da", "dutch":"nl",
            "english":"en", "finnish":"fi", "french":"fr", "german":"de",
            "greek":"el", "hindi":"hi", "italian":"it", "japanese":"ja",
            "korean":"ko", "norwegian":"no", "polish":"pl", "portugese":"pt",
            "romanian":"ro", "russian":"ru", "spanish":"es", "swedish":"sv" }

        base_url='http://ajax.googleapis.com/ajax/services/language/translate?'
        langpair='%s|%s'%(LANG.get(languageFrom.lower(),languageFrom),
                          LANG.get(languageTo.lower(),languageTo))
        params=urllib.urlencode( (('v',1.0),
                           ('q',text.encode('utf-8')),
                           ('langpair',langpair),) )
        url=base_url+params
        content=urllib2.urlopen(url).read()
        try: trans_dict=json.loads(content)
        except AttributeError:
            try: trans_dict=json.load(content)
            except AttributeError: trans_dict=json.read(content)
        return trans_dict['responseData']['translatedText']

现在在另一个名为 TestingGrounds.py 的类中，我想尝试这两种方法，但出现以下错误：

from Parser import parser

print parser.fromHtml("Hello my lady!", "English", "Italian")

Traceback（最近一次调用最后）：文件“C:\Users\Sergio.Tapia\Documents\NetBeansProjects\BabylonPython\src\TestingGrounds.py”，第 3 行，在 print parser.fromHtml("Hello my Lady!", "English", "Italian") TypeError: unbound method fromHtml() must be called with parser instance as first argument (get str instance)

Answer 1

如果你想使用 fromHtml() 作为静态方法，如果你真的不需要在解析器中访问任何数据成员，你需要这样做（为了简洁起见）

class parser:
    @staticmethod
    def fromHtml(text, languageFrom, languageTo):
         # etc.

或者，如果您希望它既是静态方法又能够成为实例方法...

class parser:
    @classmethod
    def fromHtml(self, text, languageFrom, languageTo):
         # etc.

您现在可以将其用作parser.fromHtml() 或parser().fromHtml()

查看您的代码，我应该认为您只需要一个静态方法。

Answer 2

您必须拥有parser 类的实例，而不是调用该类本身的方法。

from Parser import parser

print parser().fromHTML("Hello my lady!", "English", "Italian")

或

from Parser import parser

p = parser()
p.fromHTML(...)

或者，您可以将 fromHTML 设为静态方法：

class parser(object):   # you should probably use new-style classes
    ...
    @staticmethod
    def fromHTML(...):
        ...

然后你可以像这样使用它：

from Parser import parser

print parser.fromHTML(...)