[Python] Access outer class variable from inner class

[Frozen Forest]

It's possible to do this in Python?



class Outer:
some_var = None
def init(self, som):
self.some_var = som

class Inner:
def func(self):
Outer.some_var = 2 # don't work

[nvteighen]

It's possible to do this in Python?



class Outer:
some_var = None
def init(self, som):
self.some_var = som

class Inner:
def func(self):
Outer.some_var = 2 # don't work


That doesn't make any sense to me... The constructor should be named __init__, not init... at least if you want your class to be instantiable in the usual way, e.g. a = Outer(7).

For instance, self.some_var is a different variable than Outer.some_var... This happens because you're overwriting the variable when setting it as an instance attribute (self.some_var). Look at this:



ugi@UGI:~/Escritorio$ python
Python 2.7.2+ (default, Dec 1 2011, 01:55:02)
[GCC 4.6.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import zz # This is because of how I saved your code...
>>> a = zz.Outer(7)
>>> b = zz.Outer(3)
>>> b.some_var
3
>>> a.some_var
7
>>> a.Inner.func()
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
TypeError: unbound method func() must be called with Inner instance as first argument (got nothing instead)
>>> a.Inner().func()
>>> a.some_var
7
>>> b.some_var
3
>>>



Another problem is that with your design, func is an instance method, not a "static method"... In order to call it, one has to create an Inner instance, e.g. an anonymous one like I did above (a.Inner().func()). Otherwise, you get that TypeError exception you see above. Again, if it properly called, Inner.func has no effects because the Outer.some_var variable has been shadowed by self.some_var.

This works:


class Outer:
some_var = None
def __init__(self, som):
Outer.some_var = som

class Inner:
def func(self):
Outer.some_var = 2


However, please notice how the value now changes in both instances a and b, as expected from a class variable:



ugi@UGI:~/Escritorio$ python
Python 2.7.2+ (default, Dec 1 2011, 01:55:02)
[GCC 4.6.2] on linux2
Type "help", "copyright", "credits" or "license" for more information.
>>> import zz
>>> a = zz.Outer(3)
>>> a.some_var
3
>>> b = zz.Outer(5)
>>> b.some_var
5
>>> a.some_var
5
>>> a.Inner().func()
>>> a.some_var
2
>>> b.some_var
2
>>>


Anyway, this is terrible design... what are you trying to do?

[Frozen Forest]

Thanks thought it was related to access problem, but as your did work was I able to debug the problem to how I did use self. Since I'm new to python did I thought it was the called object and not the calling one. Anyway it's fixed now.

[emiller12345]

That is interesting. If I'm not mistaken, some_var is considered a static variable of the Outer class. Is there a simple way of making it non-static? I'm just curious...

Thanks

[nvteighen]

That is interesting. If I'm not mistaken, some_var is considered a static variable of the Outer class. Is there a simple way of making it non-static? I'm just curious...

Thanks

It is static, but when you create self.some_var, the issue is that you get a non-static variable that shadows the static one.