Python - OOPS Basics-eg1 - Day 25(4 days later)

simple program on bank account concept,based on oops

  
import datetime
import pytz
class Account:

    #this will be static method,ie it will be common for all instances(ie the class)
    #so while accessing it no need of using self
    @staticmethod
    def _current_time():
        utc_time = datetime.datetime.utcnow()
        return pytz.utc.localize(utc_time)



    def __init__(self,name,_balance):
        self._name =name
        self._transactiondetails_list = [(Account._current_time(), _balance)]
        self._balance = _balance
        print("Account Created for {}".format(self._name))
        self.showbalance()

    def deposit(self,amount):
        self._balance+=amount
        self.showbalance()
        self._transactiondetails_list.append((Account._current_time(), amount))
        # self.transactiondetails_list.append((pytz.utc.localize(datetime.datetime.utcnow()),amount))
        # print(self.transactiondetails_list)

    def withdraw(self,amount):
        if(0 < amount<=self._balance):
            self._balance-=amount
            self._transactiondetails_list.append((Account._current_time(), -amount))
        else:
            print("Amount should be greater than 0 and lesser than available balance")
        self.showbalance()

    def showbalance(self):
        print('Balance: ', self._balance)

    def showtransdetails(self):
        for date, amount in self._transactiondetails_list:
            if amount > 0:
                tran_type ='Deposited'
            else:
                tran_type ='Withdrwan'
                amount*=-1
            print("{:6} {} on {} (local time was {})".format(amount,tran_type,date,date.astimezone()))

udai = Account('udai',1000)
#udai.withdraw(100)
# udai.withdraw(200)
# udai.deposit(200)
# #we can update the balance variable to whatever we want outside of the class,so we can rename
# #to _balance,which will also dont restrict to change , but user can know that
# #it is for internal purpose and shouldn't be modified,similarly for the name and list variables
# #which should not be modified after the instantiation
# # udai.balance=0
# udai.showbalance()
# udai.showtransdetails()

#its better not to mess with '_' and '__' objects which will produce strange results
udai.showbalance()
udai._balance = 10
udai.showbalance()
print('*'*40)
print(udai.__dict__)
print(Account.__dict__)
udai.__balance = 49
udai.showbalance()
udai.showbalance()
print(udai.__dict__)
print(Account.__dict__)
 

Python - OOPS Basics - Day 25(4 days later)

Class:template for creating objects.All objects created using the same class will have the same charecteristics Objects:an instance of a class Instantiate:Create a Instance of a class Method:a funtion defined in a class Attribute:a variable bound to a instance of a class

  
#everything is objects in python
#take away : class and objects

# a = 1
# b = 3
# print (a + b)
# print (a.__add__(b))
#so + is same as __add__ ,if u ctrl right click it will goto the same definition

class kettle (object):

    power_source = 'fuel'

    def __init__(self,make,price):
        self.make = make
        self.price = price
        self.on = False

    def switch_on(self):
        self.on = True

kenwoodobj = kettle('kenwood',25)
hamilton = kettle('hamilton',30)

print(kenwoodobj.make)
print(hamilton.make)
print(hamilton.price)
hamilton.make = 'Hamiltoon'
print(hamilton.make)
print(kenwoodobj)

print ('{}={},{}={}'.format(kenwoodobj.make,kenwoodobj.price,hamilton.make,hamilton.price))
kenwoodobj1 = kenwoodobj
print(id(kenwoodobj1))
print(id(kenwoodobj))
print(id(hamilton))
print(id(hamilton.make))

#we can call the object by
#classname.objectname(instancename)
#or
#instancename.objectname()
kettle.switch_on(hamilton)
print(hamilton.make)
print(hamilton.on)
hamilton.on = False
print(hamilton.on)
hamilton.switch_on()
print(hamilton.on)

#this is called as instance variable,variable is only for this instance,not for the entire instances of the
#class
kenwoodobj.power = 1.5
print(kenwoodobj.power)
#if we try accessing the same variable for different instance,it will throw error
# print(hamilton.power)

print (kettle.power_source)
print (kenwoodobj.power_source)
print (hamilton.power_source)

print(kettle.__dict__)
print(kenwoodobj.__dict__)
print(hamilton.__dict__)

print ('*' * 80)

# kettle.power_source = 'atomic'

print (kettle.power_source)
print (kenwoodobj.power_source)
print (hamilton.power_source)

print(kettle.__dict__)
print(kenwoodobj.__dict__)
print(hamilton.__dict__)

print ('/' * 80)

#if we assign the value for the calss attribute instance,it becomes instance vriable and remains
#unaffected for the class and other instances
kenwoodobj.power_source = 'gas'

print (kettle.power_source)
print (kenwoodobj.power_source)
print (hamilton.power_source)

print(kettle.__dict__)
print(kenwoodobj.__dict__)
print(hamilton.__dict__)

print ('*' * 80)
hamilton.power_source = 'fossil fuel'

print (kettle.power_source)
print (kenwoodobj.power_source)
print (hamilton.power_source)

print(kettle.__dict__)
print(kenwoodobj.__dict__)
print(hamilton.__dict__)

hamilton.power_source = 'fuel'

print (kettle.power_source)
print (kenwoodobj.power_source)
print (hamilton.power_source)

print(kettle.__dict__)
print(kenwoodobj.__dict__)
print(hamilton.__dict__)

print ('@' * 80)

kettle.power_source = 'fuel'

print (kettle.power_source)
print (kenwoodobj.power_source)
print (hamilton.power_source)

print(kettle.__dict__)
print(kenwoodobj.__dict__)
print(hamilton.__dict__)
 

this will explain how a basic program document has to be written

  
#this will explain you how to document a program(DocString)
class song:
    """
    class to represent a song

    Attributes:
        title():The tile of the song
        artist(Artist):An artist object representing the songs creator
        duration (int):The duration of the song in seconds.May be Zero
    """
    def __int__(self,title,artist,duration=0):
        """song init method
        Args:
            title(str):Intialises the 'title' attribute
            artist(Artist):An artist object representing the songs creator
            duration (optional int):initialise value to 'duration' attribute
                    will be defaulted to zero if not specified.


        """
        self.title = title
        self.artist = artist
        self.duration = duration
 

Python - scope and recursive function - Day 25(4 days later)

this will explain the variable's scope.

  
#take way:read the document related to local,nonlocal,global
#know what is LEGB - Local Enclosing Global Builtins
#below example will illustrate the variable and the scope of it


# def spam1():
#     def spam2():
#         def spam3():
#             z = ' even more spam'
#             print('3 {}'.format(locals()))
#             return z
#         y = 'more spam '
#         y+= spam3()
#         print('2 {}'.format(locals()))
#         return y
#     x = 'spam '
#     x+= spam2()
#     print('1 {}'.format(locals()))
#     print(x)

def spam1():
    def spam2():
        def spam3():
            # y = 'test'
            z = ' even' + y
            print('3 {}'.format(locals()))
            return z
        y = ' more'+x
        y+= spam3()
        print('2 {}'.format(locals()))
        return y
    x = 'spam'
    x+= spam2()
    # we can't write like this x = 'spam' + spam2(),since spam2 function first expects x
    # it will throw unreferenced variable error if we code like that
    print('1 {}'.format(locals()))
    print(x)

print(spam1())
print(locals())
print(globals())
 

this will explain how the recursive funtion can be made use of

  
#recursive function,function that calls itself again and again
#factorial

def factorial(n):
    result = 1
    if n>1:
        for i in range (1,n+1):
            result = result * i
    return result

def factorialrec(n):
    #n factorial can also be defined as n * (n-1)!
    if n<=1:
        return 1
    else:
        return n * factorialrec(n-1)

def fibonaccirec(n):
    # Fn = Fn-1 + Fn-2
    if n<2:
        return n
    else:
        return fibonaccirec(n-1)+fibonaccirec(n-2)

def fibonacci(n):
    if n == 0:
        return 0
    if n == 1:
        return 1
    elif n==2:
        return 1
    else:
        n_minus1 = 1
        n_minus2 = 0
        for i in range(1,n):
            result = n_minus1+n_minus2
            n_minus2 = n_minus1
            n_minus1 = result
        return result




# for x in range (1,130):
#     print(x , factorial(x))

# for x in range (1,130):
#     print(x , factorialrec(x))

# here use of the recursive funtion in calculating the fibonaaci
#might slow downb the process,so we can go for direct method

# for x in range (1,36):
#     print(x , fibonaccirec(x))

#below direct method will be fast
for x in range (1,36):
    print(x , fibonacci(x))