• Operating System: Windows, 64bit
• Python Version: 3.7.11
• IDE: Jupyter Notebook (with conda env)

I have below code:

class Vocabulary(object):
    
    PAD_token = 0
    
    def __init__(self):
        self.index2word = {PAD_token: "PAD"}

# create object
voc = Vocabulary()

I want to use PAD_token class variable inside __init__ method but I got below error:

NameError                                 Traceback (most recent call last)
~\AppData\Local\Temp/ipykernel_8472/897996601.py in <module>
----> 1 voc = Vocabulary()

~\AppData\Local\Temp/ipykernel_8472/3780152240.py in __init__(self)
      4 
      5     def __init__(self):
----> 6         self.index2word = {PAD_token: "PAD", SOS_token: "SOS", EOS_token: "EOS"}

NameError: name 'PAD_token' is not defined

Question:

• How can I use PAD_token class variable inside __init__ or other methods of the class?

CodePudding user response：

There are two ways to access it

first: self.__class__.PAD_token

second: self.PAD_token

If you just need to access class variables, the first one is recommended

CodePudding user response：

To access any class variable from within the object, you need to put self. in front of the variable name.

This means that to call PAD_token you need to use self.PAD_TOKEN

Your code should look like this.

class Vocabulary(object):
    
    PAD_token = 0
    
    def __init__(self):
        self.index2word = {self.PAD_token: "PAD"}

# create object
voc = Vocabulary()

If you do not add the self it will think you are trying to access a local variable named PAD_token, and there isn't a local variable that has been defined within that method with that name, that is why it is throwing that not defined error.

CodePudding user response：

write it with self keyword like self.PAD_token.

CodePudding user response：

You are trying access variable that you assigned in your class. Here PAD_token can be called as class variable.

you can access it by class name Vocabulary.PAD_token or by self self.PAD_token.

In your case dictionary will place its value to the key i.e.

{0:"PAD"} #ignoring other keys

because you have assigned that to 0 in initialization.