Python

Question

Can someone please explain this to me
https://code.sololearn.com/ca6a12a5A114/?ref=app

Answer 1

Hi, Abdullah . What to explain?

Answer 2

What the class expression is doing

Answer 3

class expression(object):
def symbols(self):
if not hasattr(self, '_symbols'):
self._symbols = self._getsymbols()
return self._symbols
def _getsymbols(self):
"""
return type: list of strings
"""
raise NotImplementedError

Abdullah Will try to explain what I understand about it:

1. Defining the class named "expression".
2. Inheriting from the super class "object".
3. defining the method named symbols(self) and telling to interpretator this method is belongs to the "expression" class.
4. hassattr(self, '_symbols') is the built-in method in Python, parameters are  hasattr(object, name) where,

object — object name of the class

name — attribute name to be checked.

Checking in expression class if it has '_symbols' class attribute. If not has , then it will be in True.

5. Assigning the result of _getsymbols(self) method to the _symbols attribute value , we know symbols method returns True, then we can see NotImplementedError.