Class and Objects



In [1]:

    
class Animal:
    age = None



In [11]:

    
class Dog(Animal):
    pass



In [4]:

    
german_shepherd =Dog()
# making a stance ie germa nshepherd is an instnce of dog



In [5]:

    
german_shepherd









    Out[5]:





<__main__.Dog at 0x1d9e48007b8>



In [6]:

    
german_shepherd =Dog()
#it is a different instance as its menory locion shows



In [7]:

    
german_shepherd









    Out[7]:





<__main__.Dog at 0x1d9e4800a90>



In [8]:

    
german_shepherd.age =22



In [9]:

    
german_shepherd.age









    Out[9]:





22



In [12]:

    
class Dog(Animal):
    age=18



In [13]:

    
german_shepherd= Dog()



In [14]:

    
german_shepherd.age









    Out[14]:





18



In [15]:

    
german_shepherd.age =21



In [16]:

    
german_shepherd.age









    Out[16]:





21



In [17]:

    
tibetian_husky =Dog()



In [18]:

    
tibetian_husky.age









    Out[18]:





18



In [26]:

    
class Animal:
    age = None
    def is_alive(self):
        return True
    def sound(self):
        return'cry'



In [ ]:



In [27]:

    
class Cat(Animal):
    def sound(self):
        return'meow'



In [ ]:



In [28]:

    
cat=Cat()



In [29]:

    
cat.is_alive()









    Out[29]:





True



In [ ]:

    
cat.sound()

Case Study: Library Management



In [50]:

    
class Patron:
    firstname = None
    lastname = None
    address = None
    books =[]
    def __repr__(self):
        return'{} {}'.format(self.firstname,self.lastname)
    def has_book(self, bookid):
        return bookid in self.books



In [51]:

    
class Student(Patron):
    faculty =None
    year = None
    def __init__(self,firstname,lastname,faculty,year):
        self.firstname = firstname
        self.lastname = lastname
        self.faculty =faculty
        self.year = year



In [52]:

    
class Staff(Patron):
    department = None



In [53]:

    
class Book:
    bookid = None
    isbn = None
    name = None
    def __init__(self,isbn,name):
       
        self.isbn = isbn
        self.name = name
        self.bookid ='MYLIB'+':'+self.isbn
        #self must be 1st argumment
        #__ is called dunder
    def __repr__(self):
        return self.bookid



In [54]:

    
class Teacher(Patron):
    faculty = None
    def __init__(self,firstname,lastname,faculty):
        self.firstname = firstname
        self.lastname = lastname
        self.faculty =faculty



In [55]:

    
english = Book(isbn='abc-123454434',name='Learning English in 21 days')



In [56]:

    
math = Book(isbn='mth-12343435434',name='Learning math in 21 days')



In [57]:

    
nepali = Book(isbn='nep-65846324',name='Learning nepali in 21 days')



In [68]:

    
class Shelve:
    books =[]
    lended_book = []
    def is_book_available(self, bookid):
        return bookid in self.books
    def is_book_lendable(self,bookid):
        return bookid not in self.lended_books
    def borrow(self,bookid):
        
        a= input("enter book id to borrow")
        if(is_book_lendable(self,a)== True):
            lended_book.append(a)
        else:
            print('not lendable')



In [ ]:



In [61]:

    
my_library = Shelve()



In [17]:

    
# Shelve.is_book_available(my_library,'abc-123')
# we donot use this









    Out[17]:





False



In [62]:

    
my_library.is_book_available('abc-123')









    Out[62]:





False



In [63]:

    
my_library.books=[english,math,nepali]



In [64]:

    
my_library.books









    Out[64]:





[MYLIB:abc-123454434, MYLIB:mth-12343435434, MYLIB:nep-65846324]



In [65]:

    
ram=Student('ram','sharma','bct','2071')



In [66]:

    
ram









    Out[66]:





ram sharma



In [67]:

    
ram.has_book('assd')









    Out[67]:





False

homework= to borrow book and add the borrowed book to the lendedbook list



In [72]:

    
Book









    



---------------------------------------------------------------------------
TypeError                                 Traceback (most recent call last)
<ipython-input-72-2e537a01d4f8> in <module>()
----> 1 Shelve.borrow()

TypeError: borrow() missing 2 required positional arguments: 'self' and 'bookid'



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