Python 字典 pop()方法
原文:https://www.geeksforgeeks.org/python-dictionary-pop-method/
Python 字典 pop() 方法从字典中移除并返回指定的元素。
语法: dict.pop(key，def)
参数:
- 键:其键值对必须被返回和移除的键。
- def : 指定键不存在时返回的默认值。
返回:与已删除的键值对相关联的值(如果键存在)。 如果键不存在，则指定默认值。 键错误，如果键不存在且未指定默认值。
Python 字典 pop()方法示例
例 1:从词典中弹出一个元素
Python 3
# 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
Python 3
# 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
字典中没有该键时，pop()函数的行为是不同的。在这种情况下，即使不提供默认值，也会返回默认提供的值或 KeyError。
Python 3
# 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'
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