"""
Mutable and immutable objects
"""

# A mutable object is an object which can be modified in place.
# In python, everything is an object(class). So creating any variable
# will create a class instance of that object type, with a specific set of methods,
# which can operate on the object. It will also contain the content.
#
# A mutable object is an object which stays the same object, no matter what legal operation you do on it.
# There are basically 3 types of mutable objects in python.
# Lists, dictionaries and sets.
list()
dict()
set()

# What makes these objects mutable, is the fact that you can alter the content without
# altering the object itself. i.e. you can append items to a list or remove items from a list.
# The same mechanics are true for dictionaries and sets.

# Immutable objects are objects that can't be changed.
# These are some of the types which are immutable.
str()
int()
float()

# What characterisses an immutable object, is that the object itself holds the content.
# In other words, 1 value = 1 object. Take the following example.
A: int = 5
B: int = 5

# Here, we have created 2 objects 'A' and 'B', both with the integer value '5'.
# What happens in python is that when creating such objects, it will start by searching
# already created objects to see if an object with this specific value has already been
# created. If python finds that an object of this particular type and value exists, it
# will return a pointer to this object.
# That means that in our example, both 'A' and 'B' are the same object. We can prove that
# with the following. Using id() on the variable(class object) will show the internal
# python id of that object.
print(id(A))
print(id(B))

# So we can see that these objects both points to the same internal object, meaning that
# only 1 int(5) object exists, but we can have multiple varables pointing to it.
# This is exactly what immutable objects are. There can be only 1 of each.
# Now explore the following.
A: int = 5
B: int = 5
print(id(A))
print(id(B))
B += 1 # add 1 to variable 'B'
print(id(A))
print(id(B))

# What happens here?
# Now variable 'A' still points to the int(5) class object. But a new int(6) clas object
# have been created and variable 'B' now points to this object.
# The same is the case with string objects. Each string object can only contain the string
# value, it was created with.