object types, mutable or not?

[MRAB]

On 2018-05-13 21:02, Mike McClain wrote:
> I'm new to Python and OOP.
> Python  en 2.7.14 Documentation  The Python Language Reference
> 3. Data model
> 3.1. Objects, values and types
> An object's type is also unchangeable. [1]
> [1]     It is possible in some cases to change an object's type,
>      under certain controlled conditions.
> 
> It appears to me as if an object's type is totally mutable and
> solely dependant on assignment.
> 
>>>> obj = 'a1b2'
>>>> obj
> 'a1b2'
>>>> type (obj)
> <type 'str'>
>>>>
>>>> obj = list(obj)
>>>> obj
> ['a', '1', 'b', '2']
>>>> type (obj)
> <type 'list'>
>>>>
>>>> obj = dict( zip(obj[0::2],obj[1::2]) )
>>>> type (obj)
> <type 'dict'>
>>>> obj
> {'a': '1', 'b': '2'}
> 
> At what level does my understanding break down?
> 
You're not mutating an object, you're creating new objects and then 
binding them to the same name.

The name 'obj' refers to a string, then a list, etc.

BTW, you should be using Python 3 unless you really need Python 2. 
Python 2.7 is the last in the Python 2 line, and it'll not longer be 
supported after 2020.