is there a way to keep a private class variable within the class and still use it as the default value to a non-default variable (without defining that value before, outside of the class)?
example:
class a:
def __init__(self):
self.__variable = 6
def b(self, value = self.__variable):
print value
You're overthinking the problem:
class a:
def __init__(self):
self.__variable = 6
def b(self, value=None):
if value is None:
value = self.__variable
print value
self.__variable is an instance variable, not a class variable.None and adding if arg is None: arg = real_default to the function body, does work).
property wrappers now.) If I wanted that level of compile-time checking, I wouldn't be using a dynamically-typed language.It's worth adding to this that you can create a custom sentinal value that doesn't get used for any other purpose in your code if you want None to be in the range of allowable arguments. Without doing this, value, None can never be returned from b.
UseDefault = object()
# Python 3? Otherwise, you should inherit from object unless you explicitly
# know otherwise.
class a:
def __init__(self):
self._variable = 6
def b(self, value=UseDefault):
if value is UseDefault:
value = self._variable
print value
Now None can be passed to b without causing the default to be used.`
