Why is key and value not self.key and self.value?

Q&A
, ,
#1

Screen Link:

My Code: 

def put(self, key, value):
        # need self , calling a method inside a clase
        index = self._get_index(key)
        found_key = False
        for entry in self.buckets[index]:
            if entry.key == key:
                entry.value = value
                found_key = True
        if not found_key:
            self.buckets[index].append(Entry(key, value))
            self.length += 1

What I expected to happen:

What actually happened:

Replace this line with the output/error
#2

Why is key and value not self.key and self.value?

Any particular reason you think they should be self.key and self.value instead?

#3

I am confused as to why in linked lists and dictionaries for example self.length is always referenced as self.length in the code but such variables as data, key and value are not . For example, data is initialized as self.data in def init but then is referenced as data ( not self.data) in the append function.

class Node:
    def __init__(self,data):
        self.data = data
        self.prev = None
        self.next = None

class LinkedList:
        
    def __init__(self):
        self.head = None
        self.tail = None
        self.length = 0
        
    def append(self,data):
        
        new_node = Node(data)
        if self.length == 0:
            self.tail = new_node
            self.head = new_node
        else:
            self.tail = new_node
            new_node = self.tail
            self.tail = new_node
        self.length = self.length + 1
#4

That’s dependent on which values you want to persist through your Class.

self.length keeps track of the length of the Linked List, so you want its value to persist so that you can update it if you append anything to that Linked List. You could also have another method which prints the length of the Linked List for you, and in that case self.length will be storing the current length and you can use that easily to print out the length.

That’s what I mean by having it persist through the Class - it continues to store the last value it had so that you can access that anytime.

However, your key and value are just there to append those to the dictionary. Since the dictionary is storing the keys and corresponding values, you don’t need to save the key and value input arguments so that you can use them somewhere else in the Class.

Hopefully, this starts to clear it up a bit.

#5

That’s a good explanation. Thanks

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