@property decorator is used to convert methods into properties to implement the reading, setting and deletion control of properties. 1. Basic usage: define read-only attributes through @property, such as area calculated based on radius and accessed directly; 2. Advanced usage: use @name.setter and @name.deleter to implement attribute assignment verification and deletion operations; 3. Practical application: perform data verification in setters, such as BankAccount to ensure that the balance is not negative; 4. Naming specification: internal variables are prefixed, the property method name is consistent with the attribute, and unified access control is used to improve code security and maintainability.
In Python, the @property decorator is used to convert a method into a property, so that you can call it like you access a property without using parentheses. This method allows you to control the reading, setting and deletion of properties without changing the interface, and is often used for encapsulation and data verification.
Here is a simple example of @property usage:
? Basic usage: Change method to read-only attribute
class Circle:
def __init__(self, radius):
self._radius = radius
@property
def area(self):
return 3.14159 * self._radius ** 2
# Use example c = Circle(5)
print(c.area) # Output: 78.53975
# c.area = 10 # Error: Cannot assign value (read-only attribute)Here
arealooks like an attribute, but is actually calculated. The user does not need to callc.area(), justc.area.
? Advanced usage: Supports reading, setting, and deletion (getter, setter, delete)
class Person:
def __init__(self, name):
self._name = name
@property
def name(self):
print("Getting name...")
return self._name
@name.setter
def name(self, value):
if not value:
raise ValueError("Name cannot be empty")
print(f"Setting name to {value}")
self._name = value
@name.deleter
def name(self):
print("Deleting name...")
del self._name
# Use example p = Person("Alice")
print(p.name) # Output: Getting name... \n Alice
p.name = "Bob" # Output: Setting name to Bob
print(p.name) # Output: Getting name... \n Bob
del p.name # Output: Deleting name...
# print(p.name) # Error: name has been deleted? Practical application scenario: Data verification encapsulation
class BankAccount:
def __init__(self, balance):
self._balance = 0
self.balance = balance # Initialize @property with setter
def balance(self):
return self._balance
@balance.setter
def balance(self, amount):
if amount < 0:
raise ValueError("Balance cannot be negative")
self._balance = amount
# Use example acc = BankAccount(100)
print(acc.balance) # 100
acc.balance = 200
print(acc.balance) # 200
# acc.balance = -50 # Throw ValueError? Tips: Naming Specifications
- Usually, use the
_to represent "protected" internal variables (such as_name,_balance) -
@propertymethod name is the same as the property name (such asname) - Avoid direct manipulation of internal variables and always access through property control
Basically that's it. @property makes the code cleaner and safer, and is a very practical tool in object-oriented programming in Python.
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