深入讲解Python中面向对象编程的相关知识

class ClassName:
  'Optional class documentation string'
  class_suite

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 displayCount(self):
   print "Total Employee %d" % Employee.empCount

  def displayEmployee(self):
   print "Name : ", self.name, ", Salary: ", self.salary

"This would create first object of Employee class"
emp1 = Employee("Zara", 2000)
"This would create second object of Employee class"
emp2 = Employee("Manni", 5000)

emp1.displayEmployee()
emp2.displayEmployee()
print "Total Employee %d" % Employee.empCount

#!/usr/bin/python
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 displayCount(self):
   print "Total Employee %d" % Employee.empCount

  def displayEmployee(self):
   print "Name : ", self.name, ", Salary: ", self.salary"This would create first object of Employee class"
emp1 = Employee("Zara", 2000)
"This would create second object of Employee class"
emp2 = Employee("Manni", 5000)emp1.displayEmployee()
emp2.displayEmployee()
print "Total Employee %d" % Employee.empCount

Name : Zara ,Salary: 2000
Name : Manni ,Salary: 5000
Total Employee 2

emp1.age = 7 # Add an 'age' attribute.
emp1.age = 8 # Modify 'age' attribute.
del emp1.age # Delete 'age' attribute.

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'

#!/usr/bin/python
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 displayCount(self):
   print "Total Employee %d" % Employee.empCount

  def displayEmployee(self):
   print "Name : ", self.name, ", Salary: ", self.salaryprint "Employee.__doc__:", Employee.__doc__
print "Employee.__name__:", Employee.__name__
print "Employee.__module__:", Employee.__module__
print "Employee.__bases__:", Employee.__bases__
print "Employee.__dict__:", Employee.__dict__

Employee.__doc__: Common base class for all employees
Employee.__name__: Employee
Employee.__module__: __main__
Employee.__bases__: ()
Employee.__dict__: {'__module__': '__main__', 'displayCount':
<function displayCount at 0xb7c84994>, 'empCount': 2, 
'displayEmployee': <function displayEmployee at 0xb7c8441c>, 
'__doc__': 'Common base class for all employees', 
'__init__': <function __init__ at 0xb7c846bc>}

a = 40   # Create object <40>
b = a    # Increase ref. count of <40> 
c =    # Increase ref. count of <40> 

del a    # Decrease ref. count of <40>
b = 100   # Decrease ref. count of <40> 
c[0] = -1  # Decrease ref. count of <40>

#!/usr/bin/python

class Point:
  def __init( self, x=0, y=0):
   self.x = x
   self.y = y
  def __del__(self):
   class_name = self.__class__.__name__
   print class_name, "destroyed"

pt1 = Point()
pt2 = pt1
pt3 = pt1
print id(pt1), id(pt2), id(pt3) # prints the ids of the obejcts
del pt1
del pt2
del pt3

3083401324 3083401324 3083401324
Point destroyed

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

#!/usr/bin/python

class Parent:    # define parent class
  parentAttr = 100
  def __init__(self):
   print "Calling parent constructor"

  def parentMethod(self):
   print 'Calling parent method'

  def setAttr(self, attr):
   Parent.parentAttr = attr

  def getAttr(self):
   print "Parent attribute :", Parent.parentAttr

class Child(Parent): # define child class
  def __init__(self):
   print "Calling child constructor"

  def childMethod(self):
   print 'Calling child method'

c = Child()     # instance of child
c.childMethod()   # child calls its method
c.parentMethod()   # calls parent's method
c.setAttr(200)    # again call parent's method
c.getAttr()     # again call parent's method

Calling child constructor
Calling child method
Calling parent method
Parent attribute : 200

class A:        # define your class A

.....
class B:         # define your calss B

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

.....

#!/usr/bin/python

class Parent:    # define parent class
  def myMethod(self):
   print 'Calling parent method'

class Child(Parent): # define child class
  def myMethod(self):
   print 'Calling child method'

c = Child()     # instance of child
c.myMethod()     # child calls overridden method

Calling child method

#!/usr/bin/python

class Vector:
  def __init__(self, a, b):
   self.a = a
   self.b = b

  def __str__(self):
   return 'Vector (%d, %d)' % (self.a, self.b)
  
  def __add__(self,other):
   return Vector(self.a + other.a, self.b + other.b)

v1 = Vector(2,10)
v2 = Vector(5,-2)
print v1 + v2

Vector(7,8)

#!/usr/bin/python

class JustCounter:
  __secretCount = 0
 
  def count(self):
   self.__secretCount += 1
   print self.__secretCount

counter = JustCounter()
counter.count()
counter.count()
print counter.__secretCount

1
2
Traceback (most recent call last):
 File "test.py", line 12, in <module>
  print counter.__secretCount
AttributeError: JustCounter instance has no attribute '__secretCount'

.........................
print counter._JustCounter__secretCount

1
2
2