Errors in web2py book

[guruyaya]

In chapter 2, on the code example of "Special Attributes, Methods and
Operators", we have

class MyList(object)
def __init__(self, *a): self.a = a
def __len__(self): return len(self.a)
def __getitem__(self, i): return self.a[i]
def __setitem__(self, i, j): self.a[i] = j
b = MyList(3, 4, 5)
print b[1]
a[1] = 7
print b.a

1. The first line should be
class MyList(object):

2. Running line 9 of the code produces this exception:
>>> a[1] = 7
Traceback (most recent call last):
File "<stdin>", line 1, in <module>
NameError: name 'a' is not defined

I'm not sure what was intended to be demonstrated there, as even b[1]
= 7 produces an excption, but it's not working.

[b vivek]

Use this:-

class MyList(object):

    def __init__(self, *a): self.a = list(a)#this has to be a list, was a tuple earlier

    def __len__(self): return len(self.a)

    def __getitem__(self, i): return self.a[i]

    def __setitem__(self, i, j): self.a[i] = j

b=MyList(3,4,5)

print b[1]

b[1]=7#self-explanatory

print b.a

[guruyaya]

That's awsome, but it does not explain getitem. Maybe it should be:

class MyList(object):
def __init__(self, *a): self.a = list(a)

def __len__(self): return len(self.a)
def __getitem__(self, i): return self.a[i]
def __setitem__(self, i, j): self.a[i] = j

b=MyList(3,4,5)
print b[1]
b[1]=7

print b[0]

On Sep 13, 5:06 am, b vivek <bvivek1...@gmail.com> wrote:
> Use this:-
>
> class MyList(object):
>     def __init__(self, *a): self.a = list(a)#this has to be a list, was a
> tuple earlier
>     def __len__(self): return len(self.a)
>     def __getitem__(self, i): return self.a[i]
>     def __setitem__(self, i, j): self.a[i] = j
> b=MyList(3,4,5)
> print b[1]
> b[1]=7#self-explanatory
> print b.a
>