Calling a function(method) inside a class

Question

I wanted to call the function spider which is within a class with the parameters such as url,word and maxPages.

when I try calling it the following way I get an error because spider() gets more than 3 arguments (it gets 4 arguments instead).

Please can someone guide me as to how I can call the function which is within a class correctly.

My code looks like this:

    import HTMLParser
    from urllib2 import urlopen
    from pandas.io.parsers import TextParser 

    class LinkParser(HTMLParser.HTMLParser):
    #other methods

    def spider(url,word,maxPages):
        pagesTovisit = [url]
        numberVisited=0
        foundWord = False
        maxPages = 0
        while numberVisited < maxPages and pagesTovisit != [] and not foundWord:
            numberVisited = numberVisited +1


            url = pagesTovisit[0]
            pagesTovisit = pagesTovisit[1:]
            try:
                print numberVisited, "Visiting:", url
                parser = LinkParser()
                data, links = parser.getLinks(url)
                if data.find(word)>-1:
                    foundWord = True
                    pagesTovisit = pagesTovisit +links
                    print "Success"
            except:
                print "failed"
        if foundWord:
            print "the word",word,"was found at",url
        else:
            print "word not found"


    url = raw_input("enter the url: ")
    word = raw_input("enter the word to search for: ")
    maxPages = raw_input("the max pages you want to search in for are: ")

    lp=LinkParser()
    lp.spider(url,word,maxPages)

Oh look I Googled your question title and found the answer... already on StackOverflow. Hmm. — Two-Bit Alchemist, Jul 27 '16 at 14:36

Gábor Fekete · Answer 1 · 2016-07-27T14:43:10.997

3

Your indentation in the post is all wrong but I assume spider is in the class. You need to add the self keyword as first argument to the function to make it a method:

class LinkParser(HTMLParser.HTMLParser):
    def spider(self,url,word,maxPages):
         ...

Inside your spider method there is a call to LinkParser.getLinks(). Instead of creating another instance of the class you should call the method by: self.getLinks(...) as this won't create new instances. Also class methods and members can be reached inside methods by writing:

def methodOfClass(self,additionalArguments):
    self.memberName
    self.methodName(methodArguments)

edited Jul 27 '16 at 14:43

answered Jul 27 '16 at 14:35

Gábor Fekete

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I know this may be FGITW but for a complete answer you will likely want to explain how to call it as well. (Really this is a duplicate but you've already answered.) – Two-Bit Alchemist Jul 27 '16 at 14:35
The calling of the method is not changed, he can use the rest of the code unchanged. – Gábor Fekete Jul 27 '16 at 14:36
(I meant inside the class later will have to write `self.spider` -- perhaps out of scope for the question but it will be the next thing OP encounters.) – Two-Bit Alchemist Jul 27 '16 at 14:37
Oh right, I see he creates another LinkParser inside this function and uses that instead of `self.getLinks(...)`. – Gábor Fekete Jul 27 '16 at 14:39
Thanks and I apologize for the indentation. – Coolfrog Jul 27 '16 at 14:42

score 0 · Answer 2 · answered Jul 27 '16 at 14:35

0

Ignoring the indentation errors which I believe are only copy-paste issues

Every method in Python implicitly recieves the instance it is called upon as the first argument, so its definition should count for that.

Change def spider(url, word, maxPages) to def spider(self, url, word, maxPages).

answered Jul 27 '16 at 14:35

DeepSpace

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Thanks. Got it working now. – Coolfrog Jul 27 '16 at 16:08

Calling a function(method) inside a class

2 Answers2