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anupama shah
341 PointsConfusion in code :(
What is different between self.value and self as it both does the same work but Kenneth sir uses both self.value and self, Any explanation?
2 Answers
Chris Freeman
Treehouse Moderator 68,441 PointsIt is a matter of context. In the NumString class, self.value refers to the string value stored in the attribute and self refers to the NumString instance object itself.
The built-in method int() operates on strings. By using int(self) Kenneth is triggering a call to the class' __int__ method to convert to an integer. If int(self.value) were used, then the string contained in self.value would be pass directly to int(). It is important to use the int(self) to be sure that the objects own __int__ is run in cases where special considerations might be implemented for that class.
Clarification: The builtin type int can be called as a function int() to coerce and object into and integer. Internally it knows how to convert numbers and strings to integers (there is no str.__int__() method) so the __int__ method would only be called for other object types.
Ray Karyshyn
13,443 PointsHi Anupama,
In Python self represents an instance of the class.
On the other hand, self.value accesses an attribute of the class (in this case the 'value' attribute).
class Person:
name = "Bob"
def return_the_name_attribute(self):
return self.name # We retrieve attributes of a class using dot notation
Chul Kim
2,341 PointsChul Kim
2,341 PointsSelf = created object (instance)
Self.value = string object **Because we used str() on the value and saved the result (a string object) inside the variable self.value
So when we call int(self), which could also be understood as int(created object or instance), it will go to the class that the created object is under to see how to use int() on it. Which will be defined under
__int__.When we call int(self.value), which could also be understood as int(string object), we will go also go to the class that the string object is under to see how to use int() which will also be under
__int__but this one is built-in already.Is this..right?
Chris Freeman
Treehouse Moderator 68,441 PointsChris Freeman
Treehouse Moderator 68,441 PointsYou have it correct except that
int()converts a string internally. There is nostr.__int__()method. I’ve expanded my answer above.