9.4, _ del _, _ doc _, _ dict _, _ module _, _ getitem _, _ setitem _, and __,__ delitem _, _ str _, _ call __, __del ____ doc __

9.4, _ del _, _ doc _, _ dict _, _ module _, _ getitem _, _ setitem _, and __,__ delitem _, _ str _, _ call __, __del ____ doc __
_ Del __:

• Called destructor
• When an object is deleted, the python interpreter calls the _ del _ () method by default.

Import gcclass Dog (object): def _ init _ (self, name): self. name = name def _ del _ (self): print ("deleted successfully") def wang (self): print ("wang ") d1 = Dog ("") d1.wang () # d1 = None # del d1 # both of the above can be deleted, or the memory will be released after the program ends # d1.wang () # An error is reported after deletion.

 

_ Doc __:

• Class document string

Class Dog: "This is a description of this class" "def _ init _ (self, name): self. name = named1 = Dog ("Obama") # create an object and input the required Variable _ init _. By default, self automatically imports print (Dog. _ doc _) -------------------------- result: This is a description of this class.

 

_ Dict __:

• Class attributes, including class-related variables and Methods

Class Dog: # self indicates the instance of the class, representing the address of the current object def _ init _ (self, name): # It is called a class constructor, initialize the member variable self. name = name def bulk (self): ### custom function print ("% s: Wang! "% Self. name) d1 = Dog ("Obama") # create an object and input the required Variable _ init _. By default, self automatically imports print (Dog. _ dict _) ### class-related variables, function print (d1. _ dict __) # Only instance variables --------------------------------------------- {'_ module _': '_ main _', '_ init _': <function Dog. _ init _ at 0x000002B6950FC9D8>, 'bulk': <function Dog. bulk at 0x000002B6950FCA60>, '_ dict _': <attribute '_ dict _' of 'Dog 'objects>, '_ weakref __': <attribute '_ weakref _' of 'Dog 'objects>, '_ doc _': None} {'name': 'Obama '}

_ Module __:

• Module where the class definition is located: _ main __is displayed in the source file. When the class definition is imported as a module

_ Getitem __:

• If the _ getitem _ method is defined in the class, its instance object (assumed as p) can be set to a value like p [key, when the Instance Object performs the p [key] operation, the method _ getitem _ in the class is called __.

_ Setitem __:

• So that the object can use obj [key] = value to call _ setitem _ for the operation

_ Delitem __:

• Enables the object to use del obj [key] to delete attributes.

 

 

Class A (object): def _ getitem _ (self, key): print ('_ getitem _', key) def _ setitem _ (self, key, value): self. value = value print ('_ setitem _', key, value) def _ delitem _ (self, key): print ('_ delitem __', key) obj = () result = obj ['k1 '] # Trigger _ getitem _ obj ['k2'] = 'neo' # Trigger _ setitem _ print (obj. value) # You can obtain the del obj ['k1 '] # Trigger _ delitem __

 

_ Str __:

• The string that is displayed when the object is called directly.

 

class Dog(object):    def __init__(self,name):        self.name=name    def __str__(self):        return self.named=Dog("apple")print(d)

Class Dog (object): def _ init _ (self, name): self. name = name def _ str _ (self): return "Is this? "D = Dog (" apple ") print (d)

 

_ Call __:

• A class instance can also be changed to a callable object. You only need to implement a special method _ call __().

 

class call_test(object):    def __call__(self, *args, **kwargs):        print("hello ",args,kwargs)c=call_test()c()