[Tutor] __and_ and and_

[Arne Mueller]

Hi All,

I've a problem with redefining the 'and' operator for a specific class.

Here's some code that does not work:

class Bool:

    def __init__(self, list=[]):
        self.list = list

    def __and__(self, other):
        list = filter(lambda x, y=self.list: x in y, other.list)
        return Bool(list)

b = Bool([1, 2, 3, 4, 5])
a = Bool([2, 3, 10, 5])
c = a and b
print c.list
[1, 2, 3, 4, 5]

The expected result is: 
[2, 3, 5]

The following class definition works as expected:

class Bool:

    def __init__(self, list=[]):
        self.list = list

    def and_(self, other):
        list = filter(lambda x, y=self.list: x in y, other.list)
        return Bool(list)

b = Bool([1, 2, 3, 4, 5])
a = Bool([2, 3, 10, 5])
c = a.and_(b)
print c.list
[2, 3, 5]

Why doesn't the 'in-operator' '__and__' behave the same way as 'and_'?

It'd be much better object oriented desgin to say:

	c = a and b

instead
	
	c = a.and_(b) # ugly :-( 


Any explanations or better any solutions?

	thank you very much for your help,

	Arne