Python operator overloading Usage instance analysis

The example in this article describes the Python operator overloading usage. Share to everyone for your reference. Specific as follows:

In the Python language, a C + +-like operator is provided with heavy functionality:

Here's how to call the Python operator again:

Method Overloads Call for
__init__ Constructor X=class ()
__del__ Destruction of destructor objects
__add__ + x+y,x+=y
__or__ | X| Y,x|=y
__repr__ Printing Conversion Print X,REPR (X)
__str__ Printing Conversion Print x,str (X)
__call__ Call Function X ()
__getattr_ Limit X.undefine
__setattr__ value X.any=value
__getitem__ Index X[key],
__len__ length len (X)
__cmp__ comparison X==y,x<>
__lt__ less than X<>
__eq__ equals X=y.
__radd__ Right-side + +x
__iadd__ + = X+=y
__iter__ iteration for in

1. Subtraction Overload

Class Number:    def __init__ (self, start):      Self.data = Start    def __sub__ (self, Other): #minus method      Return number (self.data-other) Number  = number (x)  y = number–10 # Invoke __sub__ method class number:   def __init__ (self, start):     Self.data = Start   def __sub__ (self, Other): #minus method     return number (Self.data-o ther) Number = number (x) y = number–10 # Invoke __sub__ method

2. Iterative overloading

Class Indexer:    def __getitem__ (self, Index): #iter override      Return index * * 2 X = indexer ()  x[2] for  i In range (5):    print X[i] class indexer:   def __getitem__ (self, Index): #iter override     Return index * * 2 X = Indexer () x[2] for I in range (5):   print X[i]

3. Index overloading

Class Stepper:    def __getitem__ (self, i):      return self.data[i]  X = Stepper ()  x.data = ' Spam ' x[1] #call __g etitem__  for item in X: #call __getitem__    Print Item class Stepper:   def __getitem__ (self, i):     return to self . data[i] X = Stepper () X.data = ' Spam ' x[1] #call __getitem__ for item in X: #call __getitem__    Print Item

4. Getattr/setattr Reload

Class Empty:def __getattr__ (self,attrname): if attrname = = ' age ': Return + else:raise Attribu      Teerror,attrname X = Empty () print X.age #call__getattr__ class Accesscontrol:def __setattr__ (self, attr, value):        if attr = = ' age ': # self.attrname = value loops! SELF.__DICT__[ATTR] = value Else:print attr raise Attributeerror, attr + ' not allowed ' X = accesscontr     OL () X.age = #call __setattr__ x.name = ' Wang ' #raise exception class Empty:def __getattr__ (self,attrname): if attrname = = ' age ': return else:raise attributeerror,attrname X = Empty () print X.age #call__getattr       __ Class Accesscontrol:def __setattr__ (self, attr, value): if attr = = ' age ': # self.attrname = value loops! SELF.__DICT__[ATTR] = value Else:print attr raise Attributeerror, attr + ' not allowed ' X = Accessco Ntrol () X.age = #call __setattr__ x.name = ' Wang ' #raise exception

5. Printing overloads

Class Adder:    def __init__ (self, value=0):      self.data = value    def __add__ (self, Other):      Self.data + = Other  class Addrepr (adder):    def __repr__ (self):      return ' Addrepr (%s) '% self.data  x = Addrepr (2) #run __ init__  x + 1    #run __add__  print x   #run __repr__ class adder:   def __init__ (self, value=0):     Self.data = value   def __add__ (self, Other):     Self.data + other class Addrepr (adder):   def __repr__ (self):     return ' Addrepr (%s) '% self.data x = Addrepr (2) #run __init__ x + 1    #run __add__ print x   #run __repr__

6. Call calling function overloading

Class Prod:    def __init__ (self, value):      self.value = value    def __call__ (self, Other):      return Self.value * other  P = Prod (2) #call __init__  print P (1) #call __call__  print P (2) class Prod:   def __init__ (self, Val  UE):     self.value = value   def __call__ (self, Other):     return self.value * Other p = Prod (2) #call __init__ Print P (1) #call __call__ print P (2)

7. Destructor Overloading

Class life:    def __init__ (self, name= ' name '):      print ' Hello ', name      self.name = name    def __del__ (self ):      print ' Goodby ', self.name  brain = Life (' brain ') #call __init__  brain = ' Loretta '  # call __del__

Hopefully this article will help you with Python programming.

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