# Is and == operators works differently in python in the sense former is for the Object pointer comparision and later

# is for the values comparision. lets c by example.

a = [1, 2, 3]

b = [1, 2, 3]

print(a == b)

print(a is b)

# First prints True, but second prints False. Why lets c the object pointer to see

print(id(a), id(b))

# This prints different memory addresses i.e (4554366056, 4554366776)

# Hence, is operator always compares the id of objects not the values.

# lets take another example where the ID of objects are same.

a = [1, 2, 3]

b = a

print(a is b)

print(id(a), id(b))

# The print statement prints True because the IDs of a & b is same i.e (4449578736, 4449578736)

# __str__ & __repr__ in python class. Former is for the user & later is for the programmer by convention.

# Lets c with the example.

import datetime

today = datetime.date.today()

print(today) # It prints 2018-05-05

print(repr(today)) # It prints datetime.date(2018, 5, 5)

# In Python 2.x, __str__ returns the bytes & __unicode__ returns the characters. Hence its better to implement both

# the methods in class as:

class Test:

def __init__(self):

self.mylist = []

def adder(self, x):

if isinstance(x, list):

self.mylist.extend(x)

else:

self.mylist.append(x)

def __unicode__(self):

return u'current list {self.mylist}'.format(self=self)

def __str__(self):

return unicode(self).encode('utf-8')

myobj = Test()

myobj.adder([10, 100, 200])

print(myobj)