Classes in Python

# same variable name 'x' referring to different data types at different times

x = 10
print x

x = "Ten"
print x

x = [10, 20, 30]
print x

10
Ten
[10, 20, 30]

class Student:
    def __init__(self, name, marks):
        self.name = name
        self.marks = marks

s1 = Student("Amit", 80)
print s1.marks

s1.marks = 95  # object state changed
print s1.marks

80
95

class Student:
    # Empty class placeholder
    pass

class Student:
    def __init__(self, name, rollno):
        # Initializing data members
        self.name = name
        self.rollno = rollno

    def show(self):
        print "Name:", self.name
        print "Roll No:", self.rollno

# Object creation (__init__ is called automatically)
s1 = Student("Amit", 12)
s1.show()

Name: Amit
Roll No: 12

class Student:
    def __init__(self, name):
        self.name = name  # belongs to current object

    def display(self):
        print "Name:", self.name

s1 = Student("Amit")
s2 = Student("Ravi")

s1.display()
s2.display()

Name: Amit
Name: Ravi

class Student:
    school = "ABC School"  # class attribute

    def __init__(self, name):
        self.name = name  # instance attribute

s1 = Student("Ravi")
s2 = Student("Asha")

print Student.school
print s1.school, s1.name
print s2.school, s2.name

class Student:
    def __init__(self, name, roll):
        self.name = name
        self.roll = roll

    def __str__(self):
        # String returned here is printed for the object
        return "Student Name: " + self.name + ", Roll No: " + str(self.roll)

s1 = Student("Amit", 12)
print s1

Student Name: Amit, Roll No: 12

class Test:
    __bp = 120  # mangled attribute

t = Test()

# print t.__bp    # gives error (direct access not allowed)

# Accessing using mangled name
print t._Test__bp

120

class Demo:
    def __init__(self, name):
        self.name = name

# normal function (outside class)
def greet(self):
    print "Hello", self.name

# dynamic method addition to class
Demo.greet = greet

d1 = Demo("Ravi")
d2 = Demo("Sita")

d1.greet()
d2.greet()

Hello Ravi
Hello Sita

51
51

# Creating an object of Yourclass
YC = Yourclass(10, "ABC")

10
ABC

Runs scored are:

Traceback (most recent call last):
  File "class_in_python_q_19_a.py", line 8, in <module>
    print "Runs scored are:", runs
NameError: name 'runs' is not defined

# Corrected version: print class attributes directly
class Match:
  '"Runs and Wickets"'
  runs = 281
  wickets = 5
  def __init__(self, runs, wickets):
    self.runs = runs
    self.wickets = wickets
  print "Runs scored are:", self.runs
  print "Wickets taken are:", wickets
    
print "Test.__doc__:", Match.__doc__
print "Test.__name__:", Match.__name__
print "Test.__module__:", Match.__module__
print "Test.__bases__:", Match.__bases__
print "Test.__dict__:", Match.__dict__

Runs scored are: 281
Wickets taken are: 5
Test.__doc__: "Runs and Wickets"
Test.__name__: Match
Test.__module__: __main__
Test.__bases__: ()
Test.__dict__: {'__module__': '__main__', 'runs': 281, '__doc__': '"Runs and Wickets"', '__init__': <function __init__ at 0x14f5ed9782d0>, 'wickets': 5}

# Corrected version: print inside constructor
class Match:
  '"Runs and Wickets"'
  runs = 281
  wickets = 5
  def __init__(self, runs, wickets):
    self.runs = runs
    self.wickets = wickets
    print "Runs scored are:", self.runs
    print "Wickets taken are:", wickets
    
print "Test.__doc__:", Match.__doc__
print "Test.__name__:", Match.__name__
print "Test.__module__:", Match.__module__
print "Test.__bases__:", Match.__bases__
print "Test.__dict__:", Match.__dict__

Test.__doc__: "Runs and Wickets"
Test.__name__: Match
Test.__module__: __main__
Test.__bases__: ()
Test.__dict__: {'__module__': '__main__', 'runs': 281, '__doc__': '"Runs and Wickets"', '__init__': <function __init__ at 0x14f5ed9782d0>, 'wickets': 5}

class SOCIETY:
  # data members
  society_name = None
  flat = None
  house_no = None
  no_of_members = None
  income = None

  def __init__(self):
    self.society_name = "Surya Apartments"
    self.flat = "A Type"
    self.house_no = 20
    self.no_of_members = 3
    self.income = 25000

  def Inputdata(self):
    self.society_name = raw_input("Enter Society Name: ")
    self.house_no = int(raw_input("Enter House No: "))
    self.no_of_members = int(raw_input("Enter No. of Members: "))
    self.income = float(raw_input("Enter Income: "))
    self.allocate_flat()

  def allocate_flat(self):
    if self.income >= 25000:
      self.flat = "A Type"
    elif self.income >= 20000 and self.income < 25000:
      self.flat = "B Type"
    else:
      self.flat = "C Type"

  def Showdata(self):
    print "Society Name:", self.society_name
    print "House No:", self.house_no
    print "No. of Members:", self.no_of_members
    print "Income:", self.income
    print "Flat Type:", self.flat

# ITEMINFO class implementation
class ITEMINFO:
  ICode = None
  Item = None
  Price = None
  Qty = None
  Discount = None
  Netprice = None

  def __init__(self):
    # Initial default values
    self.ICode = 0
    self.Item = ""
    self.Price = 0
    self.Qty = 0
    self.Discount = 0
    self.Netprice = 0

  def FindDisc(self):
    # Set discount based on quantity
    if self.Qty <= 10:
      self.Discount = 0
    elif self.Qty <= 20:
      self.Discount = 15
    else:
      self.Discount = 20

  def Buy(self):
    # Read item details from user input
    self.ICode = int(raw_input("Enter Item Code: "))
    self.Item = raw_input("Enter Item Name: ")
    self.Price = float(raw_input("Enter Price: "))
    self.Qty = int(raw_input("Enter Quantity: "))
    self.FindDisc()
    # Compute final net price after discount
    total = self.Price * self.Qty
    self.Netprice = total - (total * self.Discount / 100)

  def ShowAll(self):
    # Display all data members
    print "Item Code:", self.ICode
    print "Item Name:", self.Item
    print "Price:", self.Price
    print "Quantity:", self.Qty
    print "Discount %:", self.Discount
    print "Net Price:", self.Netprice