Getting back the correct values when using classes in Python

Question

So I'm coming along in my studies into programming and Python, and am trying to write a bit of code to make a word scanner in Python. The object is to take a string of words given by the user and return a list of tuples which reads in the format (TYPE, WORD), where TYPE is the type of word it is, and WORD is the word itself. I determine the type of word by searching for the word in a group of lists containing words of that type. If the word is there, or is a number, the tuple returns the corresponding type and the word; if the word is not there, the tuple returns an "error" and the word. So for example, if the input is "My dog went north for 3 days", the list being returned would read something like:

[('error', 'My'), ('noun', 'dog'), ('error', went), 
('number', 'north'), ('error', 'for'), ('number', '3'), ('error', 'days')]

Or something like that.

Anyway, when I input the code to try and get this to work by running it from the main project directory in the command line, the only value I kept getting back in return was this message called

<__main__.scan object at 0x7fe88b5cd750>

No matter how I tried to rejuggle the code, and no matter what I tried to declare the final printed sentence as, I kept getting that main.scan object thing as the value for the string in the scanner.

Here is the code I made for reference:

from otherfunc import numconv

class scan(object):

    def __init__(self, string):
        self.string = string

    def scanner(self):
        direction = ['north', 'south', 'east', 'west', 'down',
                     'up', 'left', 'right', 'back']
        verb = ['go', 'stop', 'kill', 'eat']
        stop = ['the', 'in', 'of', 'from', 'at', 'it']
        noun = ['door', 'bear', 'princess', 'cabinet']
        words = split(self.string)
        sentence = []

        for word in words:
            if word in direction:
                analysis = ('direction', word)
                sentence.append(analysis)

            elif word in verb:
                analysis = ('verb', word)
                sentence.append(analysis)

            elif word in stop:
                analysis = ('stop', word)
                sentence.append(analysis)

            elif word in noun:
                analysis = ("noun", word)
                sentence.append(analysis)
            else:
                value = numconv(word)
                if value != None:
                    analysis = value
                    sentence.append(analysis)
                else:
                    analysis = ('error', word)
                    sentence.append(analysis)
        return sentence

string = raw_input("Type in your sentence here: ")
sentlist = scan(string)
print sentlist

And here is the code for the module I imported in the code above:

class numconv(object):

def __init__(self, s):
    self.s = s

def convert_number(self, s):
    try:
        self.value = int(s)
        return ("number", self.value)
    except ValueError:
        return None

The thing is, I've gotten the basic framework of this to work as intended in another format. In that format, I didn't declare classes and just called everything you see above in the "scan" and "numconv" classes as modules from files to run the scanner. But I'm trying to convert this into a "class" format, and trying to call the scanner as instances of "scan" classes. And so far, instead of getting the list of (TYPE, WORD) tuples I want, I just keep getting that main.scan object thing as the returned value. If anyone could be so kind, could they explain where I went wrong in my attempt to convert this into a class format, and why I only keep getting that "main.scan object" thing as the returned value when I try to call the scan class with an user-input string? Thanks.

Answer 1

In your usage of the class:

sentlist = scan(string)
print sentlist;

Your are creating an instance of the class and printing it. Instead I believe you want to call the scanner member function:

mySring = "somestring";    // declares a string 
s = scan(myString);       // creates instance of class, passing string as arg
sentlist = s.scanner();  // runs the function scanner, returning output