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Class and Instance¶

namespace¶

The attributes of a namespace are usually implemented as dict

In [1]:

class Rec(object):
    pass


rec = Rec()

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

<class '__main__.Rec'>
(<class 'object'>,)

Classes are objects in their own right, even without instance

In [2]:

class Rec(object):
    pass


print(Rec)

<class '__main__.Rec'>

Assignments to attributes of self in methods make per-instance attribues

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

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