Let's assume I have a class, with a static method, and I want a class property to be set to the value that this method returns:
class A:
@staticmethod
def foo():
return 12
baz = foo()
But doing this I get an error:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 5, in A
TypeError: 'staticmethod' object is not callable
I found a way to get around this:
class A:
class B:
@staticmethod
def foo():
return 2
baz = B.foo()
But for example if I write:
class A:
class B:
@staticmethod
def foo():
return 2
class C:
baz = B.foo()
I also get an error:
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
File "<stdin>", line 6, in A
File "<stdin>", line 7, in C
NameError: name 'B' is not defined
Is there a way to call static methods from within a class while declaring it? Why 1st and 3rd examples of code does not work but 2nd does? How python interpretor handles such declarations?
The staticmethod is a descriptor. A descriptor exposes the __get__(instance, cls) method allowing it to be accessed either through an instance or at the class level.
Now in your case you wish to call it within a class stanza. Normally this would not be possible as neither an instance nor the class are yet available. However a staticmethod ignores both in any case so you can use the following rather nasty approach to call it.
class A:
@staticmethod
def foo():
return 12
baz = foo.__get__(None, object)()
Then
>>> A.baz
12
Note: The only reason to pass object as the second argument is that staticmethod insists on being passed a class of some kind as the second argument.
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