map and self

Larry Whitley ldw at us.ibm.com
Fri Sep 15 20:10:35 CEST 2000


Never mind.  I figured out that I am supposed to be saying:

class B:
    def __init__(self):
        self.cntList = []
        for i in range(5):
            self.cntList.append( A() )
    def myprint(self):
        print map( lambda x,y=self: y.cntList[x].cnt,
range(len(self.cntList)))

Right?

Larry

"Larry Whitley" <ldw at us.ibm.com> wrote in message
news:8ptoa6$12vi$1 at news.rchland.ibm.com...
> I'm having trouble understanding "self" when used within a map().  Here's
my
> problem:
>
> class A:
>     def __init__(self):
>         self.cnt = 0
>
> class B:
>     def __init__(self):
>         self.cntList = []
>         for i in range(5):
>             self.cntList.append( A() )
>     def myprint(self):
>         print map( lambda x: self.cntList[x].cnt,
range(len(self.cntList)))
>
> >>> b = B()
> >>> b.cntList[1].cnt
> 0
> >>> b.myprint()
> Traceback (innermost last):
>   File "<interactive input>", line 1, in ?
>   File "<interactive input>", line 7, in myprint
>   File "<interactive input>", line 7, in <lambda>
> NameError: self
>
> Yet, when I perform the above actions interactively, it works as expected.
> (Note that I left "self" off here since it is inappropriate in outside the
> context of a class.)
>
> >>> cntList = []
> >>> for i in range( 5 ):
> >>>     cntList.append( A() )
> >>> len(cntList)
> 5
> >>> map( lambda x: cntList[x].cnt, range( len( cntList )))
> [0, 0, 0, 0, 0]
>
> So, my question... How do I get around the NameError: self problem and use
> this sort of thing in methods internal to a class?
>
> Larry
>
>





More information about the Python-list mailing list