Labels: Python, Class,Object

Ref:
Python Classes/Objects https://www.tutorialspoint.com/python/python_classes_objects.htm

Classes

• Creating Class
  The name of the class immediately follows the keyword class followed by a colon as follow:

class ClassName:
   'Optional class documentation string'
   class_components

Example

class Employee:
   'Common base class for all employees'
   empCount = 0
   def __init__(self, name, salary):
      self.name = name
      self.salary = salary
      Employee.empCount += 1
   def displayEmployee(self):
      print "Name : ", self.name,  ", Salary: ", self.salary

__attribute: Private attribute ('__'). Not be visible outside the class definition.

• Creating instance objects

# This would create first object of Employee class
emp1 = Employee("Zara", 2000)

• Accessing attributes and functions

emp1.displayEmployee()
print "Total Employee %d" % Employee1.empCount

object._className__attrName.: Access the private (hided) attributes.

• Attributes accessing functions

Examples:

hasattr(emp1, 'age')    # Returns true if 'age' attribute exists
getattr(emp1, 'age')    # Returns value of 'age' attribute
setattr(emp1, 'age', 8) # Set attribute 'age' at 8
delattr(empl, 'age')    # Delete attribute 'age'

• Class Built-in Attributes
  It can be accessed using dot operator.

Example:

class Employee:
  'Common base class for all employees'
  empCount = 0
  def displayEmployee(self):
     print "Name : ", self.name,  ", Salary: ", self.salary
print "Employee.__doc__:", Employee.__doc__
print "Employee.__name__:", Employee.__name__
print "Employee.__module__:", Employee.__module__
print "Employee.__bases__:", Employee.__bases__
print "Employee.__dict__:", Employee.__dict__

Result:

Employee.__doc__: Common base class for all employees
Employee.__name__: Employee
Employee.__module__: __main__
Employee.__bases__: ()
Employee.__dict__: {'__module__': '__main__',  'empCount': 2, 
'displayEmployee': <function displayEmployee at 0xb7c8441c>, 
'__doc__': 'Common base class for all employees'}

• Class Inheritance
  The child class inherits the attributes of its parent class.
  A child class can also override data members and methods from the parent.

class SubClassName (ParentClass1[, ParentClass2, ...]):
   'Optional class documentation string'
   class_suite

A class from multiple parent classes.

class A:        # define your class A
.....
class B:         # define your class B
.....
class C(A, B):   # subclass of A and B
.....

Check a relationships of two classes and instances:

• issubclass(sub, sup) returns true if the given subclass sub is indeed a subclass of the superclass sup.

• isinstance(obj, Class) returns true if obj is an instance of class Class or is an instance of a subclass of Class

• Methods Overloading

• Base Overloading Methods