如何调用以self为参数的函数？

Question

I've found some code online that may help me with a project that I'm doing, the problem is that it uses 2 parameters, one of which is self. I don't know how to all a function like that and would be really grateful if someone could explain how.

Here's the code

#code found online
def common_contexts(self, words, num=20):
    """
    Find contexts where the specified words appear; list
    most frequent common contexts first.

    :param word: The word used to seed the similarity search
    :type word: str
    :param num: The number of words to generate (default=20)
    :type num: int
    :seealso: ContextIndex.common_contexts()
    """
    if '_word_context_index' not in self.__dict__:
        #print('Building word-context index...')
        self._word_context_index = ContextIndex(self.tokens,
                                                key=lambda s:s.lower())

    try:
        fd = self._word_context_index.common_contexts(words, True)
        if not fd:
            print("No common contexts were found")
        else:
            ranked_contexts = [w for w, _ in fd.most_common(num)]
            print(tokenwrap(w1+"_"+w2 for w1,w2 in ranked_contexts))

    except ValueError as e:
        print(e)
#How I tried to call it, lines[1] is an array containing words
df=common_contexts(lines[1])
print(df)

I just want to see the output so that I can tell whether or not I can use this code in my project

Answer 1

That is a method . You are looking at the source code for nltk.text , and this is ContextIndex.common_contexts() .

You need to create an instace of the ContextIndex class, then call the method on that:

ci = ContextIndex(tokens)
df = ci.common_contexts(lines[1])

Here common_contexts is then bound to the ci instance. Calling the method then causes Python to provide a value for the self parameter; the instance on which the method was called.