# 1. 인스턴스와 클래스 차이 이해하기

'''

Instance variables are for data which is unique to every object

Class variables are for data shared between different instances of a class

'''

# 2. new style classes

'''

- Old base classes do not inherit from anything

- New style base classes inherit from object

'''

class OldClass():

def __init__(self):

print('I am an old class')

class NewClass(object):

def __init__(self):

print('I am a jazzy new class')

old = OldClass()

# Output: I am an old class

new = NewClass()

# Output: I am a jazzy new class

'''

A major advantage is that you can employ some useful optimizations like __slots__. You can use super() and descriptors and the likes.

'''

# 3. method

# __init__

# __getitem__: Implementing getitem in a class allows its instances to use the [] (indexer) operator.

class GetTest(object):

def __init__(self):

self.info = {

'name':'Yasoob',

'country':'Pakistan',

'number':12345812

}

def __getitem__(self,i):

return self.info[i]

foo = GetTest()

foo['name']

# Output: 'Yasoob'

foo['number']

# Output: 12345812

'''

Without the __getitem__ method we would have got this error:

>>> foo['name']

Traceback (most recent call last):

File "<stdin>", line 1, in <module>

TypeError: 'GetTest' object has no attribute '__getitem__'

'''