[Tutor] subscript problem

[Alan Gauld]

> class AB:
>     def __init__(self):
>         self.n_p = None
>         self.po = Vec()      # in c struct this is Vec* po
>         self.con = []        # in c struct this is short* con
>
>
> class Vec:...

> def XYZ(out):
>     n = 0
>     out.con.append(5)
>     last = out.con[n]

So last now equals 5 after the first call.

>     v_start = out.po[last]

But out is a Vec object and a Vec is not a sequence
so you can't index into it! You could if you defined a __getItem__
method which is how to override the []
operator in Python. That's why the error message says
what it does. You are trying to index into an object
which is not a sequence and doesn't provide a getItem
method.

Even if you created a list of Vec() objects you would
still get an IndexError if there were less than 5 of them.

Can you explain in words what you are trying to do with
Vec, AB etc?

Maybe we can find a more Pythonic way of doing it?

Alan G.