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Start your free trialanupama 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 68,427 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 68,427 PointsChris Freeman
Treehouse Moderator 68,427 PointsYou have it correct except that
int()
converts a string internally. There is nostr.__int__()
method. I’ve expanded my answer above.