magic methods

Examples for function built-in method

method	explanation
_doc_	The function’s documentation string, or Noneif unavailable; not inherited by subclasses	Writable
_name_	The function’s name	Writable
_qualname_	The function’s qualified nameNew in version 3.3.	Writable
_module_	The name of the module the function was defined in, or None if unavailable.	Writable
_defaults_	A tuple containing default argument values for those arguments that have defaults, or None if no arguments have a default value	Writable
_code_	The code object representing the compiled function body.	Writable
_globals_	A reference to the dictionary that holds the function’s global variables — the global namespace of the module in which the function was defined.	Read-only
_dict_	The namespace supporting arbitrary function attributes.	Writable
_closure_	None or a tuple of cells that contain bindings for the function’s free variables. See below for information on the cell_contents attribute.	Read-only

python

def myfunction(arg1 = 1):
    """ My function example"""
    # test string
    test = 'test_string'

python

1	myfunction.__doc__

' My function example'

python

1	myfunction.__name__

'myfunction'

python

1	myfunction.__qualname__

'myfunction'

python

1	myfunction.__module__

'__main__'

python

1	myfunction.__defaults__

(1,)

python

1	myfunction.__code__

<code object myfunction at 0x0000020E0443AB70, file "<ipython-input-1-d45fff7bc581>", line 1>

python

1	myfunction.__dict__

{}

python

1	myfunction.__closure__

Examples for class built-in method

python

class MyClass(object):
    ''' My class example'''
    def __init__ (self):
        self.a = 0
        self.b = 'test'
    def __new__(cls):
        print('Creating new instance')
        return super(MyClass, cls).__new__(MyClass)
    def __del__(self):
        print('Deleting instance')
    def __str__(self):
        return 'Ass hole class'
    def __getattr__(self, attr):
        print('No such attribute!')
        raise AttributeError
    def __setattr__(self, attr, value):
        self.__dict__[attr] = 1

Class methods:

python

1	dir(MyClass)

['__class__',
 '__del__',
 '__delattr__',
 '__dict__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattr__',
 '__getattribute__',
 '__gt__',
 '__hash__',
 '__init__',
 '__init_subclass__',
 '__le__',
 '__lt__',
 '__module__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 '__weakref__']

python

1	MyClass.__class__

type

python

1	MyClass.__bases__

(object,)

python

1	MyClass.__dict__

mappingproxy({'__module__': '__main__',
              '__doc__': ' My class example',
              '__init__': <function __main__.MyClass.__init__(self)>,
              '__new__': <staticmethod at 0x20e045c0be0>,
              '__del__': <function __main__.MyClass.__del__(self)>,
              '__str__': <function __main__.MyClass.__str__(self)>,
              '__getattr__': <function __main__.MyClass.__getattr__(self, attr)>,
              '__setattr__': <function __main__.MyClass.__setattr__(self, attr, value)>,
              '__dict__': <attribute '__dict__' of 'MyClass' objects>,
              '__weakref__': <attribute '__weakref__' of 'MyClass' objects>})

Instance methods:

python

1	test_instance = MyClass()

Creating new instance

python

1	dir(test_instance)

['__class__',
 '__del__',
 '__delattr__',
 '__dict__',
 '__dir__',
 '__doc__',
 '__eq__',
 '__format__',
 '__ge__',
 '__getattr__',
 '__getattribute__',
 '__gt__',
 '__hash__',
 '__init__',
 '__init_subclass__',
 '__le__',
 '__lt__',
 '__module__',
 '__ne__',
 '__new__',
 '__reduce__',
 '__reduce_ex__',
 '__repr__',
 '__setattr__',
 '__sizeof__',
 '__str__',
 '__subclasshook__',
 '__weakref__',
 'a',
 'b']

python

1	test_instance.__dict__

{'a': 1, 'b': 1}

python

1	test_instance.__doc__

' My class example'

python

1	test_instance.__init__.__code__

<code object __init__ at 0x0000020E044FD8A0, file "<ipython-input-31-5e1debc8af67>", line 3>

python

1	test_instance.__setattr__.__doc__

Note: _del_() is NOT directly called when deleting instance. It has to be called eplicitely!

python

1	test_instance.__del__()

Deleting instance

python

1	print(test_instance)

Ass hole class

python

1	test_instance.__str__()

'Ass hole class'

The correspondence between operator symbols and method names is as follows:

Code

x<y calls x.__lt__(y),
x<=y calls x.__le__(y),
x==y calls x.__eq__(y),
x!=y calls x.__ne__(y),
x>y calls x.__gt__(y),
and x>=y calls x.__ge__(y).

python

object.__lt__(self, other)
object.__le__(self, other)
object.__eq__(self, other)
object.__ne__(self, other)
object.__gt__(self, other)
object.__ge__(self, other)

_getattr_(self, attr) only gets called when attribute is not found

python

1	test_instance.d

No such attribute!



---------------------------------------------------------------------------

AttributeError                            Traceback (most recent call last)

<ipython-input-45-4c7135cdd908> in <module>
----> 1 test_instance.d


<ipython-input-31-5e1debc8af67> in __getattr__(self, attr)
     13     def __getattr__(self, attr):
     14         print('No such attribute!')
---> 15         raise AttributeError
     16     def __setattr__(self, attr, value):
     17         self.__dict__[attr] = 1


AttributeError:

python

1	test_instance.a

_setattr_ will do things when setting a value.

python

1	test_instance.d = 4

python

1	test_instance.d