#!/usr/bin/env python
# coding: utf-8

# # Class and Instance
# 
# 
# ## namespace
# The attributes of a namespace are usually implemented as dict
# 
# - **`__class__`**: The link to its class (instance)
# - **`__bases__`**: A tuple of references to their superclasses (class)

# In[1]:


class Rec(object):
    pass


rec = Rec()

print(rec.__class__)
print(Rec.__bases__)


# ## Class Object (Default Behavior)
# 1. Assignments inside **class** make class attributes
# 3. Class Attributes provid object state and behavior
# 
# Classes are objects in their own right, even without instance

# In[2]:


class Rec(object):
    pass


print(Rec)


# ## Instance Object (Concrete Items)
# Assignments to attributes of **self** in methods make per-instance attribues

# ## Attribute
# - When looking for a name, Python checks the instance, then its class, then all superclasses
# - Each *object.attribute* reference invokes a new, independent search.

# ---

# # Operator Overloading
# - Methods named with double underscores(**`__x__`**)
#     - Not built-in or reserved words, just attributes
#     - Can be called directly by your code
#         - e.g. **`x.__init__`** is often called manually to trigger initialization in a superclass
# - Classes may override most built-in type operations
# - No defaults for operator overloading methods
# - Not are required
# - New-style classes (detail in next chapter) have some defaults, but not for commom operations
#     
# - It's an optinal feature.  
# - Used primarily by people developing tools for other Python programmers, not by application developers  
# - Overloaded operators should work the same way that built-in operator
# 
# ## Why Operator Overloading?
# - Mathematical in nature
# - Expect the operators available on a built-in type like a list or a dict
# - Mimic the built-in types