Brief introduce the python object built-in method

1. Python Object 101
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2. Python 3.7.1
• dir(object())
• __format__、__repr__、__str__、__doc__
• __dir__、__hash__、__sizeof__
• __delattr__、__setattr__、__getattribute__
• __eq__、__ge__、__gt__、__le__、__lt__、__ne__
• __class__、__new__、__init__
• __ini_subclass__、__subclasshook__
• __reduce__、__reduce_ex__

3. String Related
• __repr__、__str__
• builtin function：repr、str
• __doc__
• builtin function：help
• testing library：doctest
• __format__
• builtin function：format

4. Object Property
• __dir__
• builtin function：dir
• __hash__
• builtin function：hash
• __sizeof__
• the internal size of the object in bytes

5. Object Attribute
• __setattr__、__delattr__
• similar the builtin function - setattr and delattr
• __getattribute__
• Called unconditionally
• call __getattr__ next if - 1) raise AttributeError or 2) direct call
• __getattr__
• will NOT call if attribute can be get by normal mechanism

6. Comparison
• __eq__、__ge__、__gt__、__le__、__lt__、__ne__
• ==、>=、>、<、<=、!=

7. Object Instance
• __class__
• the class to which a instance belongs
• after 3.5 __class__ is writable
• __new__
• object.__new__ is a static method
• create and return a new object
• __init__
• The first method called when instance created

8. Metaclass in Python
• __metaclass__
• https://stackoverflow.com/questions/100003/what-
are-metaclasses-in-python

9. Inheritance
• __init_subclass__
• call when inherited, event not initialization
• __subclasshook__
• return True、False、NotImplementedError
• check is subclass or not

10. Python Serialization
• __reduce__
• return the String or the Tuple
• string names a global variable
• tuple must be between two or three
• first is callable and second is the argument
• __reduce_ex__
• protocol version

11. Pickle Security
• REC - Remote Code Execution
• https://blog.nelhage.com/2011/03/exploiting-pickle/

12. More __XXX__
• basic arithmetic operator and comparison
• slice and list indexing
• …

13. First Class Citizen
• First-Class Object / First-Class Citizen
• Pass to other variable, function
• As the return value
• Can created in run-time
• Exist without assigned name