Python dict pop()用法及代码示例

Python语言为几乎所有容器(无论是列表容器还是集合容器)指定了pop()。这篇特别的文章着重说明Python词典提供的pop()方法。这种方法对于经常处理字典的程序员很有用。

用法：dict.pop(key, def)

参数：
key:必须返回并删除其键值对的键。
def:如果指定的键不存在，则返回的默认值。

返回：
如果存在键，则与已删除键/值对关联的值。
如果不存在 key ，则指定为默认值。
KeyError，如果不存在 key 且未指定默认值。

代码1：演示工作pop()，当存在 key 时。

# 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}

的行为pop()当字典中不存在该键时，函数会有所不同。在这种情况下，如果没有提供默认值，它将返回提供的默认值或KeyError。

代码2：演示pop()在没有 key 的情况下的工作

# 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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注：本文由纯净天空筛选整理自manjeet_04大神的英文原创作品 Python Dictionary | pop() method。非经特殊声明，原始代码版权归原作者所有，本译文未经允许或授权，请勿转载或复制。