In a previous post _ (private) vs. __ (name mangling), we covered python's implementation of methods similar to "private" in Java. In this post, we will use python to implement getter & setter similar to Java.
For example, we want to use setter and getter to access the cat's name.
class Cat:
def __init__(self, name):
self._name = name
def getName(self):
return self._name
def setName(self, new_name):
self._name = new_name
cat = Cat("mimi")
cat.setName("dada")
print(cat.getName()) # dadaSeems perfect, but python provides @property to achieve a more pythonic approach!
@property is a decorator that returns results in real time based on class variables, but it cannot be modified at this time. If you want to change the property (and variables with the property), then use @variable_name.setter.
class Cat:
def __init__(self, name):
self.name = name # <-------- 1
@property
def name(self):
print("getter triggered")
return self._name
@name.setter
def name(self, new_name): # <--- 2
print("setter triggered")
self._name = new_name
cat = Cat("mimi") # setter triggered
cat.name = "dada" # setter triggered
print(cat.name) # getter triggered
# dadaIn the above example, the self.name in __init__ is actually a call to @name.setter, which stores the name into the private variable _name. Then if an instance calls .name, then the private variable _name is actually retrieved from property name().
The first example of using @property is to enhance password security.
When creating the User instance, the given password goes into the setter to generate an encrypted hash password, and then store it into password_hash. Now you can't get the password with user_instance.password.
To authenticate that the password is correct, use the new function verify_password to verify that the input password hash is the same as password_hash.
class User:
def __init__(self, password):
self.password = password
@property
def password(self):
raise AttributeError("password is not readable.")
@password.setter
def password(self, password):
self.password_hash = generate_password_hash(password)
def verify_password(self, password):
return check_password_hash(self.password_hash, password)The second use of @property is to access variables in an observer-like manner.
For example, below, the fullname property will be changed along with the first_name and last_name of the class. We can also use fullname.setter to change the first_name and last_name of a fullname.
class User:
def __init__(self, first_name, last_name):
self.first_name = first_name
self.last_name = last_name
@property
def fullname(self):
return f"{self.first_name} {self.last_name}"
@fullname.setter
def fullname(self, fullname):
self.first_name, self.last_name = fullname.split(" ")
user = User("Mimi", "Wang")
print(user.fullname) # Mimi Wang
user.first_name = "Sansan"
print(user.fullname) # Sansan Wang
user.fullname = "Dada Wang"
print(user.fullname) # Dada Wang
print(user.first_name) # Dada| Article | Link |
|---|---|
| [Python] setter 和 getter | https://medium.com/bryanyang0528/python-setter-%E5%92%8C-getter-6c08a9d37d46 |
| [Python教學]@property是什麼? 使用場景和用法介紹 | https://www.maxlist.xyz/2019/12/25/python-property/ |
| Python OOP Tutorial 6: Property Decorators - Getters, Setters, and Deleters | https://www.youtube.com/watch?v=jCzT9XFZ5bw |