Python setattr()

內置函數setattr()用於將給定值賦給指定對象的指定屬性。

 **setattr(object, name, value)** #where object indicates whose attribute value is needs to be change 

setattr()參數:

取三個參數。我們可以說setattr()相當於 object.attribute = value。

setattr()返回值

setattr()方法不返回任何東西，它只分配對象屬性值。這個函數在動態編程中很有用，在這種情況下，我們不能使用「點」運算符來分配屬性值。

Python 中setattr()方法的示例

示例setattr()在 Python 中是如何工作的？

 class PersonName:
    name = 'Dany'

p = PersonName()
print('Before modification:', p.name)

# setting name to 'John'
setattr(p, 'name', 'John')

print('After modification:', p.name) 

輸出:

Before modification: Dany
After modification: John

示例 2:當在setattr()中找不到屬性時

 class PersonName:
    name = 'Dany'

p = PersonName()

# setting attribute name to John
setattr(p, 'name', 'John')
print('Name is:', p.name)

# setting an attribute not present in Person
setattr(p, 'age', 23)
print('Age is:', p.age) 

輸出:

Name is: John
Age is: 23 

示例 3: Python setattr()異常情況

 class PersonName:

    def __init__(self):
        self._name = None

    def get_name(self):
        print('get_name called')
        return self._name

    # for read-only attribute
    name = property(get_name, None)

p = PersonName()

setattr(p, 'name', 'Sayooj') 

輸出:

Traceback (most recent call last):
  File "/Users/sayooj/Documents/github/journaldev/Python-3/basic_examples/python_setattr_example.py", line 39, in <module>setattr(p, 'name', 'Sayooj')
AttributeError: can't set attribute</module>