Python: How to get Outer class variables from inner static class?

Question

I want to specify variable once by making instance Outer(variable), than this variable use in all static classes, how should I do that? Is there any other solution than use not static methods and pass Outer into each inner class?

class Outer():
    def __init__(self, variable):
        self.variable= variable

    class Inner1():        
        @staticmethod
        def work1():
            **print Outer.variable**

    class Inner2():        
        @staticmethod
        def work2():
            **print Outer.variable**

Why the heck would you want inner classes or hand-made static classes in Python? There's no advantage. Python is not Java (and not C# either). Also, you seem to conflate instance variables (some_obj.attr) with class ("static") variables (SomeClass.attr). — user395760
– user395760, Commented May 31, 2012 at 19:50
Guido van Rossum on static methods: "They're basically an accident -- back in the Python 2.2 days when I was inventing new-style classes and descriptors, I meant to implement class methods but at first I didn't understand them and accidentally implemented static methods first. Then it was too late to remove them and only provide class methods." — Sven Marnach
– Sven Marnach, Commented May 31, 2012 at 19:51
for example in pyqt is using of static methods very often, riverbankcomputing.co.uk/static/Docs/PyQt4/html/… - getSaveFileName(), etc. — Meloun
– Meloun, Commented May 31, 2012 at 20:03
@Meloun That's because it's a binding to the C++ API which defines Qt. But in Python, there are few reasons for them, and module-level functions are far more idiomatic for most uses. Also, as another comment notes, classmethod is simply better. — user395760
– user395760, Commented May 31, 2012 at 20:23

jayven huangjunwen · Accepted Answer · 2012-06-01 04:08:47Z

2

If you really want such thing, metaclass may help a little, for example:

from types import ClassType

class OuterMeta(type):
    def __new__(mcls, name, base, attr):
        ret = type.__new__(mcls, name, base, attr)
        for k, v in attr.iteritems():
            if isinstance(v, (ClassType, type)):
                v.Outer = ret
        return ret

class Outer(object):
    __metaclass__ = OuterMeta
    var = 'abc'    
    class Inner:
        def work(self):
            print self.Outer.var
        @classmethod
        def work2(cls):
            print cls.Outer.var

then

>>> Outer.Inner.work2()
abc

answered Jun 1, 2012 at 4:08

jayven huangjunwen

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Ignacio Vazquez-Abrams · Accepted Answer · 2012-05-31 19:49:00Z

1

No. Inner-class methods have no way of accessing instances of the outer class.

answered May 31, 2012 at 19:49

Ignacio Vazquez-Abrams

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