TypeError: name 'peek' is not defined

#1

Hello again!

So, I’ve coded my parser and tested it to make sure everything is working. Now, I’m trying to implement it using object-oriented programming and see if I like this way more, as opposed to solely using methods. Admittedly, I think there’s considerable overlap between the two.

I came across an error with my skip() method. Here’s my code:


class Parse(object):

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

    def peek(self):
        return self.word_list[0]

    def match(self, expecting):
        word = self.word_list.pop(0)

        if word[0] == expecting:
            return word
        else:
            return None

    def skip(self):
        while self.peek() == 'stop':
            match(self.word_list, 'stop')

As I was creating a nosetest to test all of my methods, I encountered an issue with my skip() method. A TypeError was being thrown, saying that the name ‘peek’ was not defined. The solution was simple: I needed to add self right before I implemented peek() in the skip() method. I noticed we did this in Exercise 43 as well with our scene_map (I think?), where we were first introduced to object-oriented programming.

So, why the need to use self in this instance? Is it because we’re calling it on an instance of the Parse class?

#2

Easy, you have to use self.peek to talk about peek. Same for skip and match.

#3

Right, I figured. Thanks!