Python字典 pop() 方法

Python字典 pop()方法从字典中移除并返回指定元素。

Syntax : dict.pop(key, def)

Parameters : 

• key : The key whose key-value pair has to be returned and removed.
• def : The default value to return if specified key is not present.

Returns : Value associated to deleted key-value pair, if key is present. 
Default value if specified if key is not present. 
KeyError, if key not present and default value not specified. 

Python Dictionary pop() 方法示例

示例 1：从字典中弹出一个元素

Python3

# Python 3 code to demonstrate
# working of pop()
 
# initializing dictionary
test_dict = {"Nikhil": 7, "Akshat": 1, "Akash": 2}
 
# Printing initial dict
print("The dictionary before deletion : " + str(test_dict))
 
# using pop to return and remove key-value pair.
pop_ele = test_dict.pop('Akash')
 
# Printing the value associated to popped key
print("Value associated to poppped key is : " + str(pop_ele))
 
# Printing dictionary after deletion
print("Dictionary after deletion is : " + str(test_dict))

输出 ：

The dictionary before deletion : {'Nikhil': 7, 'Akshat': 1, 'Akash': 2}
Value associated to poppped key is : 2
Dictionary after deletion is : {'Nikhil': 7, 'Akshat': 1}

示例 2： Python字典弹出第一个元素

Python3

# Python 3 code to demonstrate
# working of pop()
 
# initializing dictionary
test_dict = {"Nikhil": 7, "Akshat": 1, "Akash": 2}
 
# Printing initial dict
print("The dictionary before deletion : " + str(test_dict))
 
# using pop to return and remove key-value pair.
pop_first = test_dict.pop("Nikhil")
 
# Printing the value associated to popped key
print("Value associated to poppped key is : " + str(pop_first))
 
# Printing dictionary after deletion
print("Dictionary after deletion is : " + str(test_dict))

输出：

The dictionary before deletion : {'Nikhil': 7, 'Akshat': 1, 'Akash': 2}
Value associated to poppped key is : 7
Dictionary after deletion is : {'Akshat': 1, 'Akash': 2}

示例 3：弹出字典中不存在的元素

当键不在字典中时，pop()函数的行为是不同的。在这种情况下，它返回默认提供的值或 KeyError，以防即使没有提供默认值。

Python3

# Python 3 code to demonstrate
# working of pop() without key
 
# initializing dictionary
test_dict = {"Nikhil": 7, "Akshat": 1, "Akash": 2}
 
# Printing initial dict
print("The dictionary before deletion : " + str(test_dict))
 
# using pop to return and remove key-value pair
# provided default
pop_ele = test_dict.pop('Manjeet', 4)
 
# Printing the value associated to popped key
# Prints 4
print("Value associated to poppped key is : " + str(pop_ele))
 
# using pop to return and remove key-value pair
# not provided default
pop_ele = test_dict.pop('Manjeet')
 
# Printing the value associated to popped key
# KeyError
print("Value associated to poppped key is : " + str(pop_ele))

输出 ：

The dictionary before deletion : {'Nikhil': 7, 'Akshat': 1, 'Akash': 2}
Value associated to poppped key is : 4
Traceback (most recent call last):
  File "main.py", line 20, in 
    pop_ele = test_dict.pop('Manjeet')
KeyError: 'Manjeet'