What exactly does "AttributeError: temp instance has no attribute '__getitem__'" mean?

Question

I'm trying to understand a problem I'm having with python 2.7 right now.

Here is my code from the file test.py:

class temp:
 def __init__(self):
  self = dict()
  self[1] = 'bla'

Then, on the terminal, I enter:

from test import temp
a=temp

if I enter a I get this:

>>> a
<test.temp instance at 0x10e3387e8>

And if I try to read a[1], I get this:

>>> a[1]
Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
AttributeError: temp instance has no attribute '__getitem__'

Why does this happen?

Answer 1

First, the code you posted cannot yield the error you noted. You have not instantiated the class; a is merely another name for temp. So your actual error message will be:

TypeError: 'classobj' object has no attribute '__getitem__'

Even if you instantiate it (a = temp()) it still won't do what you seem to expect. Assigning self = dict() merely changes the value of the variable self within your __init__() method; it does not do anything to the instance. When the __init__() method ends, this variable goes away, since you did not store it anywhere else.

It seems as if you might want to subclass dict instead:

class temp(dict):
    def __init__(self):
        self[1] = 'bla'