Python Cracked #2

This post has to do with Python variable binding (the way I understand it).

All variables are binded (point) to an object or None.

Everything is an object (numbers, strings, classes, modules, functions,etc.) 

A variable can point to any type of object.

Some objects are mutable (can be changed); some are immutable (cannot be changed).

Example mutable objects: lists, dictionaries

Example immutable objects: strings,  numbers of any type ,  tuples 

 

x = 1 ( var x points to integer object with value of 1)

x= x + 1 ( var x points to a different integer object with value of 2)

The original object x was bound to is  now unbound and will be removed by the garbage collector.

If x pointed to a list object and it was changed,  x would still point to the same object.

 

Variables as function parameters:

• A pointer is passed to the original object for each parameter.
• If the parameter object is immutable, then any changes will cause creation of a new object.
• The variable used in the calling statement will still point to the original (unchanged) object. 
• If the parameter object is mutable, then any changes will affect the original object.
• The variable used in the calling statement will see affects of the changes made.