Whenever I create an instance of a class, create a variable that's assigned that first instance, and use an attribute of the class on the second variable my first variable changes.
class number:
def __init__(self, value):
self.value = value
def add(self):
self.value = self.value + 1
a = number(10)
b = a
b.add()
a.value
why does a.value give me 11 when I didn't use a.add()?
@juanpa.arrivillaga provided good comments to your question. I just want to add how to fix your code to do what you expect it to do:
class number:
def __init__(self, value):
self.value = value
def add(self):
self.value = self.value + 1
a = number(10)
b = number(a.value) # create a new object with the same value as 'a'
b.add()
a.value
import copy
class number:
def __init__(self, value):
self.value = value
def add(self):
self.value = self.value + 1
a = number(10)
b = copy.copy(a) # make a shallow copy of the object a
# b = copy.deepcopy(a) # <-- that is what most people think of a "real" copy
b.add()
a.value
Because when you do b = a you're not creating a new object of the class number just passing the reference of the object which a references.
a is ba = 1 ; b = a ; a += 1; print(a, b) ; # 2, 1a. The point is because ints are immutablebia not affected.