定義 Python 中類變數的正確方式是什麼?


類變數是在__init__方法外部宣告的變數。它們是靜態元素,這意味著它們屬於類而不是類例項。這些類變數由該類的所有例項共享。類變數的示例程式碼 

例項

class MyClass:
  __item1 = 123
  __item2 = "abc"
  def __init__(self):
    #pass or something else

透過更多程式碼,你會有更清晰的瞭解 −

class MyClass:
    stat_elem = 456
    def __init__(self):
        self.object_elem = 789
c1 = MyClass()
c2 = MyClass()
# Initial values of both elements
>>> print c1.stat_elem, c1.object_elem
456 789
>>> print c2.stat_elem, c2.object_elem
456 789
# Let's try changing the static element
MyClass.static_elem = 888
>>> print c1.stat_elem, c1.object_elem
888 789
>>> print c2.stat_elem, c2.object_elem
888 789
# Now, let's try changing the object element
c1.object_elem = 777
>>> print c1.stat_elem, c1.object_elem
888 777
>>> print c2.stat_elem, c2.object_elem
888 789

更新於: 2020-01-03

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