Error: self not found

Question

So I tried this:

class X:
def __init__(self, y):
self.y = y
def setY(self, y=self.y):
self.y = y

My idea was to set a first value with the instantiation and have a setter to change it later. In case the user enters nothing, I wanted to keep the original value.

Now why is this not working?

Answer 1

HonFu
Maybe this will help:

https://stackoverflow.com/a/5555470

"It doesn't work because default arguments are evaluated at function definition time, not at call time"

also here:

https://stackoverflow.com/a/8131960

"You can't really define this as the default value, since the default value is evaluated when the method is defined which is before any instances exist."

Answer 2

self is not recognized as a parameter

Try setting default value of None and inside the setter you can use "or" to go to the default value if y is None

class X:
def __init__(self, y):
self.y = y
def setY(self, y=None):
self.y = y or self.y

x = X(42)
print(x.y)
x.setY()
print(x.y)

Answer 3

Burey hm, okay, interesting.

I had seen something like that behaviour in functions but never really understood it. Not sure if I do now, but at least it's consistent, that already helps a lot.

Thank you!

Answer 4

Burey, that definitely works, but I am wondering why this even gives an error, I find it surprising.

In other areas, like in the or-part of a boolean or an else that never happens, it has no effect to write an unknown name (since depending on the program flow it might later be known).

Since I will later instantiate my object and deliver a self.y, shouldn't the class (logically) be lenient and allow it?