使用 __init__ 方法更新对象的实例
[英]Updating an instance of an object with the __init__ method
问题描述
Reusing the __init__<\/code> method to change attributes' values
重用__init__<\/code>方法来改变属性的值<\/h3>Python 3.10 on Windows 64bit<\/em> Windows 64 位上的 Python 3.10<\/em>
Let's say I have a class that has an update<\/code> method which calls the __init__<\/code> method.假设我有一个类，它有一个调用__init__<\/code>方法的update<\/code>方法。 The update<\/code> method is created to avoid multiple line assignments of the attributes.创建update<\/code>方法是为了避免属性的多行分配。
重用__init__<\/code>方法来改变属性的值<\/h3>Python 3.10 on Windows 64bit<\/em> Windows 64 位上的 Python 3.10<\/em>
Let's say I have a class that has an update<\/code> method which calls the __init__<\/code> method.假设我有一个类，它有一个调用__init__<\/code>方法的update<\/code>方法。 The update<\/code> method is created to avoid multiple line assignments of the attributes.创建update<\/code>方法是为了避免属性的多行分配。
class Person: def __init__(self, name: str, age: int): self.name = name self.age = age def update(self, **attributes): self.__init__(**attributes)<\/code><\/pre>Object instantiation:<\/strong>对象实例化：<\/strong>
p = Person(name="Alex", age=32) print(p.name, p.age) >> Alex 32<\/code><\/pre>Object reference before:<\/strong>之前的对象参考：<\/strong>
print(p) >> <__main__.Person object at 0x0000028B4ED949A0><\/code><\/pre>Calling for the update method:<\/strong>调用更新方法：<\/strong>
p.update(name="Sam", age=80) print(p.name, p.age) >> Sam 80<\/code><\/pre>Object reference after:<\/strong>之后的对象引用：<\/strong>
print(p) >> <__main__.Person object at 0x0000028B4ED949A0><\/code><\/pre>Clearly, the reference hasn't changed!<\/strong>显然，参考没有改变！<\/strong>
Obviously the actual use of this is for large objects that has multiple parameters and get frequently modified at once as internal reactions.
2 个解决方案
解决方案1
0 已采纳 2022-02-05 19:23:03
__init__<\/code> , unlike __new__<\/code> , doesn't deal with memory references at all. __init__<\/code>与__new__<\/code>不同，根本不处理内存引用。 self<\/code> is already a valid object produced by __new__<\/code> which __init__<\/code> initializes. self<\/code>已经是由__init__<\/code>初始化的__new__<\/code>生成的有效对象。
You can do it the other way round for clarity:为了清楚起见，您可以反过来做：
class Person:
def __init__(self, name: str, age: int):
# Signal to whoever will read your code
# that the class is supposed to have these attributes
self.name = None
self.age = None
self.update(name=name, age=age)
def update(self, name: str, age: int):
self.name = name
self.age = age
解决方案2
0 2022-02-05 21:24:48
in addition to ForceBru's answer if wanted如果需要的话，除了 ForceBru 的回答
class Person:
def __init__(self, name: str, age: int):
self.name = name
self.age = age
def update(self, **attributes):
for attribute, value in attributes.items():
if hasattr(self,attribute):
setattr(self, attribute, value)
else:
raise AttributeError(f'{self.__name__} has no attribute: {attribute}')
x = Person(name='Henry',age=12)
print(f'name={x.name}, age={x.age}')
x.update(name='Joe')
print(f'name={x.name}, age={x.age}')
x.update(name='Kyle',age=20)
print(f'name={x.name}, age={x.age}')
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