Python delattr() and del()用法及代碼示例

德萊特

delattr()方法用於在對象的事先許可下從對象中刪除命名屬性。句法：

delattr(object, name)

The function takes only two parameter:

object: from which 
the name attribute is to be removed.
name: of the attribute 
which is to be removed.

The function doesn't returns any value, 
it just removes the attribute, 
only if the object allows it.

工作方式：假設我們有一個名為Geek的類，它有5個學生作為屬性。因此，使用delattr()方法，我們可以刪除任何一個屬性。

# Python code to illustrate delattr()
class Geek:
  stu1 = "Henry"
  stu2 = "Zack"
  stu3 = "Stephen"
  stu4 = "Amy"
  stu5 = "Shawn"
 
names = Geek()
 
print('Students before delattr()--')
print('First = ',names.stu1)
print('Second = ',names.stu2)
print('Third = ',names.stu3)
print('Fourth = ',names.stu4)
print('Fifth = ',names.stu5)
 
# implementing the method
delattr(Geek, 'stu5')
 
print('After deleting fifth student--')
print('First = ',names.stu1)
print('Second = ',names.stu2)
print('Third = ',names.stu3)
print('Fourth = ',names.stu4)
# this statement raises an error
print('Fifth = ',names.stu5)

輸出：

Students before delattr()--
First =  Henry
Second =  Zack
Third =  Stephen
Fourth =  Amy
Fifth =  Shawn
After deleting fifth student--
First =  Henry
Second =  Zack
Third =  Stephen
Fourth =  Amy

當執行移至程序的最後一行時，即，調用第五個屬性時，編譯器將引發錯誤：

Traceback (most recent call last):
  File "/home/028e8526d603bccb30e9aeb7ece9e1eb.py", line 25, in 
    print('Fifth = ',names.stu5)
AttributeError:'Geek' object has no attribute 'stu5'

del運算符

Python中還有另一個運算符，其作用與delattr()方法類似。它是del運算符。讓我們看看它是如何工作的。

# Python code to illustrate del()
class Geek:
  stu1 = "Henry"
  stu2 = "Zack"
  stu3 = "Stephen"
  stu4 = "Amy"
  stu5 = "Shawn"
 
names = Geek()
 
print('Students before del--')
print('First = ',names.stu1)
print('Second = ',names.stu2)
print('Third = ',names.stu3)
print('Fourth = ',names.stu4)
print('Fifth = ',names.stu5)
 
# implementing the operator
del Geek.stu5
 
print('After deleting fifth student--')
print('First = ',names.stu1)
print('Second = ',names.stu2)
print('Third = ',names.stu3)
print('Fourth = ',names.stu4)
# this statement raises an error
print('Fifth = ',names.stu5)

輸出：

Students before del--
First =  Henry
Second =  Zack
Third =  Stephen
Fourth =  Amy
Fifth =  Shawn
After deleting fifth student--
First =  Henry
Second =  Zack
Third =  Stephen
Fourth =  Amy

結果是一樣的，但有一個錯誤：

Traceback (most recent call last):
  File "/home/7c239eef9b897e964108c701f1f94c8a.py", line 26, in 
    print('Fifth = ',names.stu5)
AttributeError:'Geek' object has no attribute 'stu5'

德爾VS delattr()

1. 動態刪除：del是更明確和有效的，並且delattr()允許動態屬性刪除。
2. Speed:如果考慮並運行以上程序，則執行速度之間會有細微差別。與delattr()相比，del稍快一些，具體取決於機器。
3. 字節碼說明：與delattr()相比，del還占用更少的字節碼指令。

因此，我們通過說del比delattr快一點來結束比較，但是當涉及到屬性的動態刪除時，delattr()具有優勢，因為del運算符無法實現。