1, Classes and objects

Example 1

class Employee:
   'Base class of employee'
   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
 
# Create the first instance
emp1 = Employee("Zhang San", 8000)
# Create the second instance
emp2 = Employee("Li Si", 15000)
emp1.displayEmployee()
emp2.displayEmployee()
print "Total Employee : %d" % Employee.empCount

Operation result:

Name : Zhang San, Salary : 8000
Name: Li Si, Salary : 15000
Total Employee : 2

analysis:
(1) Init is a constructor. In C++/Java, the constructor name is the same as the class name, while in Python, the constructor name is "init"__
(2) Self, which is equivalent to this in C + + or Java, is a pointer. When an instance is created, self points to the instance
(3) name and salary are instance variables and empCount are class variables
(4) C++/Java needs to use the new keyword to create an instance, Python does not
(5) The second percent sign in the last line, comma in C/C + +

2, Python's built-in class properties

__dict: properties of a class (including a dictionary, which consists of data properties of the class)
__doc: the document string of the class
 __Name: class name
 __Module: the module where the class definition is located (the full name of the class is' main '. Classname', if the class is in an import module mymod, then the classname. Module is equal to mymod)
__bases: all the parent elements of a class (including a tuple of all the parent classes)

Example 2

class Employee:
   'Base class of employee'
   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
 
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__

Operation result:

Employee.__doc__: Base class of employee
Employee.__name__: Employee
Employee.__module__: __main__
Employee.__bases__: ()
Employee.__dict__: 
{'displayEmployee': <function displayEmployee at 0x10a93caa0>,
'__module__': '__main__', 
'empCount': 0,
'__doc__': ' Base class of employee ',
'__init__': <function __init__ at 0x10a939578>}