what.py

In [1]: def x(object):
   ...:     def __init__(self):
   ...:         self.x = 12
   ...:         

In [2]: print(x.x)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-2-a981fbbe4431> in <module>()
----> 1 print(x.x)

AttributeError: 'function' object has no attribute 'x'

In [3]: class x(object):
   ...:     def __init__(self):
   ...:         self.x = 12
   ...:         

In [4]: print(x.x)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-4-a981fbbe4431> in <module>()
----> 1 print(x.x)

AttributeError: type object 'x' has no attribute 'x'

In [5]: class x(object):
   ...:     x = 12
   ...:     def __init__(self):
   ...:         self.x = 12
   ...:         
   ...:         

In [6]: print(x.x)
12

In [7]: print(x.__init__.x)
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-7-49b4f6efc396> in <module>()
----> 1 print(x.__init__.x)

AttributeError: 'function' object has no attribute 'x'

In [8]: class x:
   ...:     def __init__(self):
   ...:         self.y = 5
   ...:         z = 1
   ...:         

In [9]: a = x()

In [10]: x.y
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-10-24e477bb360e> in <module>()
----> 1 x.y

AttributeError: type object 'x' has no attribute 'y'

In [11]: print(a.y)
5

In [12]: class x(object):
    ...:     def __init__(self):
    ...:         self.y = 5
    ...:         z = 1
    ...:         

In [13]: a = x()

In [14]: a.y
Out[14]: 5

In [15]: class x(object):
    ...:     def __init__(self):
    ...:         self.x = 12
    ...:         

In [16]: class x(object):
    ...:     def __init__(self):
    ...:         self.s = 12
    ...:         
    ...:         

In [17]: x.s
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-17-035fe37d29c3> in <module>()
----> 1 x.s

AttributeError: type object 'x' has no attribute 's'

In [18]: a = x()

In [19]: a.s
Out[19]: 12

In [20]: