class method in details

class method in details

In python class method invocation should be done with care because it is little different from Java.

3 types of method can be defined in a class

1. Instance method: This methods are the method for which class instance is passed implicitly as an argument. 

2. Class method: This methods are the method for which caller class is passed implicitly as an argument. 

We need to use decorator @classmethod to define this inside a class.

3. Static method: This methods are the method for which neither class nor instance is passed implicitly as an argument. 

We need to use decorator @staticmethod to define this inside a class.

In below I have given one example class.

===start of class_example.py==

class A:

   def __init__(self,name,org='init_xyz'):

      print "start constructor"

      self.name=name

      self.org=org

      self.age=10

      print "end constructor"

   def instanceMethod(self):

      print "start of instanceMethod"

      print self.name,self.org

      print "End of instanceMethod"

   @classmethod

   def class_method(ownClass, cls):

      print "start class_method"

      print cls.name,cls.org

      print "End of class_method"

   @staticmethod

   def static_method(name,org='static_xyz'):

      print "start static_method"

      print name,org

      print "End of static_method"

a=A('james')

print "output of instanceMethod: calling using instance..."

a.instanceMethod()

b=A('Thor','ABC')

print "output of class_method: calling using syntax a.methodName(...)"

a.class_method(b)

print "output of class_method: calling using syntax A.methodName(a,...)"

A.class_method(b)

====end of class_example.py==

Output:

[root@xxxx pyws]# python class_example.py

start constructor

end constructor

output of instanceMethod: calling using instance...

start of instanceMethod

james init_xyz

End of instanceMethod

start constructor

end constructor

output of class_method: calling using syntax a.methodName(...)

start class_method

Thor ABC

End of class_method

output of class_method: calling using syntax A.methodName(a,...)

start class_method

Thor ABC

End of class_method