Python - 检查是否存在对应于 K 键的特定值

给定一个字典列表，检查特定的键值对是否存在。

Input : [{“Gfg” : “4”, “is” : “good”, “best” : “1”}, {“Gfg” : “9”, “is” : “CS”, “best” : “10”}], K = “Gfg”, val = “find” 
Output : False 
Explanation : No value of “Gfg” is “find”.

Input : [{“Gfg” : “4”, “is” : “good”, “best” : “1”}, {“Gfg” : “9”, “is” : “CS”, “best” : “10”}], K = “Gfg”, val = 4 
Output : True 
Explanation : 4 present as “Gfg” value. 
 

方法#1：使用列表理解

这是可以执行此任务的方法之一。在这里，我们使用列表推导来提取字典，然后使用“in”运算符来检查它是否有任何值。

Python3

# Python3 code to demonstrate working of
# Check if particular value is present corresponding to K key
# Using list comprehension
 
# initializing lists
test_list = [{"Gfg" : "4", "is" : "good", "best" : "1"},
             {"Gfg" : "find", "is" : "better", "best" : "8"},
             {"Gfg" : "9", "is" : "CS", "best" : "10"}]
 
# printing original list
print("The original list : " + str(test_list))
 
# initializing K key
K = "Gfg"
 
# initializing target value
val = "find"
 
# extracting values using list comprehension
# using in operator to check for values
res = val in [sub[K] for sub in test_list]
     
# printing result
print("Is key-val pair present?  : " + str(res))

输出

The original list : [{'Gfg': '4', 'is': 'good', 'best': '1'}, {'Gfg': 'find', 'is': 'better', 'best': '8'}, {'Gfg': '9', 'is': 'CS', 'best': '10'}]
Is key-val pair present?  : True

方法#2：使用 map() + in运算符

这是可以执行此任务的另一种方式。在这个获取与特定键对应的值的任务中，使用 map() 执行，将函数扩展到每个字典。

蟒蛇3

# Python3 code to demonstrate working of
# Check if particular value is present corresponding to K key
# Using map() + in operator
 
# initializing lists
test_list = [{"Gfg" : "4", "is" : "good", "best" : "1"},
             {"Gfg" : "find", "is" : "better", "best" : "8"},
             {"Gfg" : "9", "is" : "CS", "best" : "10"}]
 
# printing original list
print("The original list : " + str(test_list))
 
# initializing K key
K = "Gfg"
 
# initializing target value
val = "find"
 
# extracting values using map
# using in operator to check for values
res = val in list(map(lambda sub : sub[K], test_list))
     
# printing result
print("Is key-val pair present?  : " + str(res))

输出

The original list : [{'Gfg': '4', 'is': 'good', 'best': '1'}, {'Gfg': 'find', 'is': 'better', 'best': '8'}, {'Gfg': '9', 'is': 'CS', 'best': '10'}]
Is key-val pair present?  : True