Why does this not work?

x = 100
print(self.x)

I understand that self keyword refers to the variables in the current class. So I used this in the __main__ class, right? So why does it throw an error?

The error is as given below:

Traceback (most recent call last):
  File "/home/kali/Documents/pythonClassPractice/test.py", line 3, in <module>
    print(self.x)
          ^^^^
NameError: name 'self' is not defined