How to add property to a class dynamically?

Question

The goal is to create a mock class which behaves like a db resultset.

So for example, if a database query returns, using a dict expression, {\'ab\':100, \'cd\'

Answer 1

You don't need to use a property for that. Just override __setattr__ to make them read only.

class C(object):
    def __init__(self, keys, values):
        for (key, value) in zip(keys, values):
            self.__dict__[key] = value

    def __setattr__(self, name, value):
        raise Exception("It is read only!")

Tada.

>>> c = C('abc', [1,2,3])
>>> c.a
1
>>> c.b
2
>>> c.c
3
>>> c.d
Traceback (most recent call last):
  File "", line 1, in 
AttributeError: 'C' object has no attribute 'd'
>>> c.d = 42
Traceback (most recent call last):
  File "", line 1, in 
  File "", line 6, in __setattr__
Exception: It is read only!
>>> c.a = 'blah'
Traceback (most recent call last):
  File "", line 1, in 
  File "", line 6, in __setattr__
Exception: It is read only!