Dynamic addition of attributes and methods for python classes and instances, and dynamic addition of python instances

Dynamic addition of attributes and methods for python classes and instances, and dynamic addition of python instances

From types import MethodType
# Python is a dynamic language, so it can dynamically add attributes and methods to classes and instances.
# However, note: The method for dynamically adding an instance is only valid for this instance and invalid for other instances.
# However, the method added to the class is valid for the instances generated by the class.
Class Student (object ):
Pass

S = Student ()
S. name = "zrs" # Add dynamic attributes to the class
S. age = 22
Print (s. name)
Print (s. age)

Def set_age (self, age ):
Self. age = age
Return self. age

# The first parameter is the method to be added, and the second parameter is the Instance name.
S. set_age = MethodType (set_age, s) # use this function to add classes or instances.
Print (s. set_age (25 ))

Def set_name (self, name ):
Self. name = name

# Dynamically add methods to a class
Student. set_name = set_name
S1 = Student ()
S1.name = "zhognrongshun"
S1.age = 22
S1.set _name ("666 ")
Print (s1.name)

# It is a good thing that dynamic languages can dynamically add attributes and methods.
# What if I have to restrict the attributes of an instance?
Class Student2 (object ):
_ Slots _ = ("name", "age") # Only attributes can be added here

S11 = Student2 ()
S11.name = "zlzl"
S11.age = 22
# S11.score = 99 # error: 'student2' object has no attribute 'score'
Print (s11.name, s11.age)




# This is the second way to dynamically Add a class
# Create a method
Def set_age (self, arg ):
Self. age = arg
# Create a class
Class Student3 (object ):
Pass
# Directly use a class to create a method, but at this time it is still linked to create a method in the memory outside the class
Student3.set _ age = MethodType (set_age, Student3)
# At this time, when creating an instance, the external method set_age will also copy these instances and Student3 class will point to the same set_age Method
S21 = Student1 ()
S21.set _ age (60)
Print (s21.age) # view results