Python decorator method and decorator property All In One

Python decorator method and decorator property All In One

修饰器/装饰器；静态方法；实例方法; 属性方法;

• @classmethod decorator
• @staticmethod decorator
• @property decorator

# cls
class Rectangle:
  def __init__(self, width, height):
    self.width = width
    self.height = height
  # 实例方法
  def calculate_area(self):
    return self.width * self.height
  # 类方法 (类似 js 的 static method)
  @classmethod
  def new_square(cls, side_length):
    return cls(side_length, side_length)

# 类方法
square = Rectangle.new_square(5)
print("类方法", square.calculate_area())

# 类实例方法
s = Rectangle(3, 3)
print("类实例方法", s.calculate_area())

"""
$ py3 ./classmethod-decorator.py

类方法 25
类实例方法 9

"""

# static

class Pizza:
  def __init__(self, toppings):
    self.toppings = toppings
  # 静态方法
  @staticmethod
  def validate_topping(topping):
    if topping == "pineapple":
      # raise ValueError("No pineapples!")
      return False
    else:
      return True

ingredients = ["cheese", "onions", "spam"]

# all()
if all(Pizza.validate_topping(i) for i in ingredients):
  pizza = Pizza(ingredients)
  print("🍕pizza =", pizza)


bug = "pineapple"

print("🍍pineapple", Pizza.validate_topping(bug))

"""

$ py3 ./staticmethod-decorator.py
🍕pizza = <__main__.Pizza object at 0x10c527fa0>
🍍pineapple False

"""

@property decorator

# property

class Pizza:
  def __init__(self, toppings):
    self.toppings = toppings
  # 只读属性方法
  @property
  def pineapple_allowed(self):
    return False
  # 普通方法
  def get_pineapple_flag(self, flag = False):
    self._flag = flag
    return flag

pizza = Pizza(["cheese", "tomato"])

# 直接读取属性，直接调用属性名称
print(pizza.toppings)

# 间接读取属性，直接调用方法名称 + 括号
print(pizza.get_pineapple_flag())
print(pizza.get_pineapple_flag(True))
print(pizza._flag)

# 只读属性，仅省略了一个方法调用的括号 💩
print("✅ 只读属性 ", pizza.pineapple_allowed)

# AttributeError: can't set attribute ❌
pizza.pineapple_allowed = True
# print(pizza.pineapple_allowed)


"""

$ py3 ./class-property-decorator.py

['cheese', 'tomato']
False
True
True
✅ 只读属性  False
Traceback (most recent call last):
  File "/Users/xgqfrms-mm/Documents/github/Python-3.x-All-In-One/src/class-property-decorator.py", line 29, in <module>
    pizza.pineapple_allowed = True
AttributeError: can't set attribute
"""

• property getter
• property setter

# setter/getter

class Pizza:
  def __init__(self, toppings):
    self.toppings = toppings
    self._pineapple_allowed = False

  @property
  def pineapple_allowed(self):
    return self._pineapple_allowed

  # property setter
  @pineapple_allowed.setter
  def pineapple_allowed(self, value):
    if value:
      password = input("Enter the password: ")
      if password == "123":
        self._pineapple_allowed = value
      else:
        raise ValueError("Alert! Intruder!")
  @pineapple_allowed.getter
  def pineapple_allowed(self):
    return "✅" + str(self._pineapple_allowed)

try:
  pizza = Pizza(["cheese", "tomato"])
  print(pizza.toppings)
  print(pizza._pineapple_allowed)
  print("\npizza.pineapple_allowed =", pizza.pineapple_allowed)
  pizza.pineapple_allowed = True
  print(pizza.pineapple_allowed)
except ValueError:
  print("ValueError")
finally:
  print("finished")

"""

$ py3 ./class-property-setter-getter.py

['cheese', 'tomato']
False

pizza.pineapple_allowed = ✅False
Enter the password: 123
✅True

"""

demos

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python all function

all(iterable)

Return True if all elements of the iterable are true (or if the iterable is empty).
Equivalent to:

def all(iterable):
    for element in iterable:
        if not element:
            return False
    return True

https://docs.python.org/3/library/functions.html#all

https://www.w3schools.com/python/ref_func_all.asp

refs

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