Function in a python class that is not a method

Question

I have a class that needs auxiliary functions, e.g. one to calculate a checksum that just uses the passed in arguments and not any properties of the class. This function is only called by the class's methods. So I dont need to pass in the 'self' as the first formal of the function.

How should I implement these functions? Can I have non-method functions in a class? Should I define them outside the class (even though they are not used by anything else)? Or is it ok for them to be regular methods?

Answer 1

Just do a nested function:

class Foo(object):
    def bar(self, arg):
        def inner(arg):
            print 'Yo Adrian imma in inner with {}!'.format(arg)

        inner(arg)    

Foo().bar('argument')      

Or just ignore the self:

class Foo(object):

    def prive(_, arg):
        print 'In prive with {}!'.format(arg)


    def bar(self, arg):
        def inner(arg):
            print 'Yo Adrian imma in inner with {}!'.format(arg)

        inner(arg)   
        self.prive(arg)

    def foo(self,arg):
        self.prive(arg)     

Foo().bar('argument')
Foo().foo('another argument') 

Second example prints:

Yo Adrian imma in inner with argument!   
In prive with argument!
In prive with another argument!