Python|密钥未知时从字典中删除项目

字典是一个无序、可变和索引的集合。在Python中，字典是用大括号编写的，它们有键和值。它广泛用于日常编程、Web 开发和机器学习。

让我们讨论在密钥未知时从字典中删除项目的各种方法。

方法 #1：使用 naive + del

del关键字可用于就地删除字典中存在的键。可以考虑使用它的一个缺点是，如果找不到密钥，则会引发异常，因此必须处理不存在的密钥。

# Python code to demonstrate how to remove 
# an item from the dictionary without knowing 
# a key using naive + del method
  
# Initialising dictionary
test1 = {"akshat" : 21, "nikhil" : 22, "akash" : 23, "manjeet" : 27}
  
# Printing dictionary before removal 
print ("Original Dictionary : " + str(test1))
  
# using naive + del method
# remove key nikhil
item_to_remove = 23
  
for key, item in test1.items():
    if item is item_to_remove:
        del test1[key]
        break
          
# Printing dictionary after removal 
print ("Dictionary after remove is : " + str(test1))

输出：

Original Dictionary : {'akshat': 21, 'manjeet': 27, 'nikhil': 22, 'akash': 23}
Dictionary after remove is : {'akshat': 21, 'manjeet': 27, 'nikhil': 22}

方法#2：使用字典理解。

# Python code to demonstrate how to remove 
# item from dictionary without knowing key
# using dictionary comprehension
  
# Initialising dictionary
test1 = {"akshat" : 21, "nikhil" : 22, "akash" : 23, "manjeet" : 27}
  
# Printing dictionary before removal 
print ("Original Dictionary : " + str(test1))
  
# using dictionary comprehension method
# remove key akash
value_to_remove = 23
  
res = {key: value for key, value in test1.items() 
             if value is not value_to_remove}
          
# Printing dictionary after removal 
print ("Dictionary after remove is : " + str(res))

输出：

Original Dictionary : {'nikhil': 22, 'akash': 23, 'akshat': 21, 'manjeet': 27}
Dictionary after remove is : {'nikhil': 22, 'manjeet': 27, 'akshat': 21}

方法 #3：使用 naive + pop() + naive

Python语言为几乎所有容器指定了pop() ，无论是列表、集合等。

# Python code to demonstrate how to remove
# item from dictionary without knowing key
# using naive + pop()
  
# Initialising dictionary
test1 = {"akshat" : 21, "nikhil" : 22, "akash" : 23, "manjeet" : 27}
  
# Printing dictionary before removal 
print ("Original dictionary : " + str(test1))
  
# using naive + pop()
# remove key akash
value_to_remove = 23
  
for key in test1.keys():
    if test1[key] == value_to_remove:
        test1.pop(key)
        break
          
# Printing dictionary after removal 
print ("Dictionary after remove is : " + str(test1))

输出：

Original dictionary : {'manjeet': 27, 'nikhil': 22, 'akshat': 21, 'akash': 23}
Dictionary after remove is : {'manjeet': 27, 'nikhil': 22, 'akshat': 21}