I have a class and a function that tries to update and return instances of this class:
class Foo:
def __init__(self):
self.datum = 'a'
def update(self):
self.datum = 'b' if self.datum == 'a' else 'a'
def updater(foo_obj):
return( foo_obj.update() )
but calling updater() returns Nones and not instances of class Foo. Why is this? What can I change to get the desired result?
type(updater(Foo())) #NoneType
Update method updater.
def updater(foo_obj):
foo_obj.update()
return( foo_obj )
OR return self from class function:
def update(self):
self.datum = 'b' if self.datum == 'a' else 'a'
return self
.update(), which is None.Your update method does not return anything, which in Python means that it implicitly returns None. If you want it to have a meaningful return value, you'd have to do so explicitly. E.g.:
def update(self):
self.datum = 'b' if self.datum == 'a' else 'a'
return self.datum
If you'd like update to return instances of the Foo class, you have to explicitly have it do so with a return statement, otherwise it will implicitly return None (i.e. it's a void method, even though Python doesn't use these terms because duck-typing). Do this like so:
def update(self):
self.datum = 'b' if self.datum == 'a' else 'a'
return self
You could also return the Foo object in updater if you don't want your class to do it, like so:
def updater(foo_obj):
foo_obj.update()
return foo_obj
If you'd like to return just self.datum and not the whole object, then do that like:
def update(self):
self.datum = 'b' if self.datum == 'a' else 'a'
return self.datum
or similarly:
def updater(foo_obj):
foo_obj.update()
return foo_obj.datum
Foo.update.