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，功能会有所不同。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'