Python string assignment issue!

Question

So I'm fairly new to Python but I have absolutely no idea why this strong oldUser is changing to current user after I make the parse call. Any help would be greatly appreciated.

while a < 20:
    f = urllib.urlopen("SITE")
    a = a+1

    for i, line in enumerate(f):
        if i == 187:
            print line

            myparser.parse(line)
            if fCheck == 1:
                result  = oldUser[0] is oldUser[1]
                print oldUser[0]
                print oldUser[1]
            else:
                result = user is oldUser

            fCheck = 1
            print result

            user = myparser.get_descriptions(firstCheck)

            firstCheck = 1
            print user

            if result:
                print "SAME"
                array[index+1] = array[index+1] +0
            else:
                oldUser = user

        elif i > 200:
            break
        myparser.reset()

I don't understand why result doesn't work either... I print out both values and when they're the same it's telling me they're not equal... Also, why does myparser.parse(line) turn oldUser into a size 2 array? Thanks!

** Here's the definition for myparse...

class MyParser(sgmllib.SGMLParser):
"A simple parser class."

def parse(self, s):
    "Parse the given string 's'."
    self.feed(s)
    self.close()

def __init__(self, verbose=0):
    "Initialise an object, passing 'verbose' to the superclass."

    sgmllib.SGMLParser.__init__(self, verbose)
    self.divs = []
    self.descriptions = []
    self.inside_div_element = 0

def start_div(self, attributes):
    "Process a hyperlink and its 'attributes'."

    for name, value in attributes:
        if name == "id":
            self.divs.append(value)
            self.inside_div_element = 1

def end_div(self):
    "Record the end of a hyperlink."

    self.inside_div_element = 0

def handle_data(self, data):
    "Handle the textual 'data'."

    if self.inside_div_element:
        self.descriptions.append(data)


def get_div(self):
    "Return the list of hyperlinks."

    return self.divs

def get_descriptions(self, check):
    "Return a list of descriptions."
if check == 1:
    self.descriptions.pop(0)
    return self.descriptions

Post all of your code. What you posted can't even run. Look at 'fCheck' vs. 'firstCheck'. — Michael Kent
– Michael Kent, Commented May 2, 2011 at 23:43

Josh Lee · Accepted Answer · 2011-05-02 22:48:47Z

5

Don’t compare strings with is. That checks if they’re the same object, not two copies of the same string. See:

>>> string = raw_input()
hello
>>> string is 'hello'
False
>>> string == 'hello'
True

Also, the definition of myparser would be useful.

answered May 2, 2011 at 22:48

Josh Lee

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1 Comment

Michael Over a year ago

Ahhhh i see... thank you! but do you know why saying user = myparse.get_descriptions() is also changing oldUser? myparse.get_descriptions() returns the user name that I want in taht line of HTML

Community · Accepted Answer · 2017-05-23 12:29:06Z

1

I'm not quite sure what your code is doing, but I suspect you want to use == instead of is. Using is compares object identity, which is not the same as string equality. Two different string objects may contain the same sequence of characters.

result = oldUser[0] == oldUser[1]

If you're curious, for more information on the behaviour of the is operator see Python “is” operator behaves unexpectedly with integers.

edited May 23, 2017 at 12:29

CommunityBot

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answered May 2, 2011 at 22:49

Greg Hewgill

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