In [3]:

    

# modify instance action

class IntTuple(tuple):
    def __init__(self, iterable):
        print('in init', self, iterable)

    def __new__(cls, iterable):
        print('in new', cls.__name__, iterable)
        g = (x for x in iterable if (isinstance(x, int) and x > 0))
        return super(IntTuple, cls).__new__(cls, g)


    

In [4]:

    

t = IntTuple([1, -1, 'abc', ['x', 'y'], 6, 3])
t


    

    




in new IntTuple [1, -1, 'abc', ['x', 'y'], 6, 3]
in init (1, 6, 3) [1, -1, 'abc', ['x', 'y'], 6, 3]






    
Out[4]:





(1, 6, 3)

In [32]:

    

# Decrease the memory use of instances of a class

class Player0(object):
    def __init__(self, uid, name, status=0, level=1):
        self.uid = uid
        self.name = name
        self.stat = status
        self.level = level

        
class Player1(object):
    __slots__ = ['uid', 'name', 'stat', 'level']
    def __init__(self, uid, name, status=0, level=1):
        self.uid = uid
        self.name = name
        self.stat = status
        self.level = level


    

In [33]:

    

p0 = Player0(uid='0000', name='Allen')
p1 = Player1(uid='0001', name='Bob')


    

In [35]:

    

set(dir(p0)) - set(dir(p1))


    

    
Out[35]:





{'__dict__', '__weakref__'}

In [36]:

    

p0.__dict__


    

    
Out[36]:





{'level': 1, 'name': 'Allen', 'stat': 0, 'uid': '0000'}

In [37]:

    

p0.x='123'


    

In [38]:

    

p0.__dict__


    

    
Out[38]:





{'level': 1, 'name': 'Allen', 'stat': 0, 'uid': '0000', 'x': '123'}

In [39]:

    

p0.__dict__['y']=99


    

In [40]:

    

p0.y


    

    
Out[40]:





99

In [41]:

    

p0.__dict__


    

    
Out[41]:





{'level': 1, 'name': 'Allen', 'stat': 0, 'uid': '0000', 'x': '123', 'y': 99}

In [42]:

    

del p0.__dict__['x']


    

In [43]:

    

p0.x


    

    




---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-43-83311df61857> in <module>()
----> 1 p0.x

AttributeError: 'Player0' object has no attribute 'x'

In [44]:

    

del p0.y


    

In [45]:

    

p0.y


    

    




---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-45-156d4a11b74e> in <module>()
----> 1 p0.y

AttributeError: 'Player0' object has no attribute 'y'

In [46]:

    

p0.__dict__


    

    
Out[46]:





{'level': 1, 'name': 'Allen', 'stat': 0, 'uid': '0000'}

In [47]:

    

import sys


    

In [49]:

    

p1.x=2


    

    




---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
<ipython-input-49-be0c278d57cf> in <module>()
----> 1 p1.x=2

AttributeError: 'Player1' object has no attribute 'x'

In [53]:

    

sys.getsizeof(p0.__dict__)


    

    
Out[53]:





864

In [54]:

    

sys.getsizeof(p1.__slots__)


    

    
Out[54]:





96