Python語言為幾乎所有容器(無論是列表容器還是集合容器)指定了pop()。這篇特別的文章著重說明Python詞典提供的pop()方法。這種方法對于經常處理字典的程序員很有用。

用法：dict.pop(key, def)

參數：

key:必須返回并刪除其鍵值對的鍵。

def:如果指定的鍵不存在，則返回的默認值。

返回：

如果存在鍵，則與已刪除鍵/值對關聯的值。

如果不存在 key ，則指定為默認值。

KeyError，如果不存在 key 且未指定默認值。

代碼1：演示工作pop()，當存在 key 時。

# 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))

輸出：

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}

的行為pop()當字典中不存在該鍵時，功能會有所不同。在這種情況下，如果沒有提供默認值，它將返回提供的默認值或KeyError。

代碼2：演示pop()在沒有 key 的情況下的工作

# 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))

輸出：

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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