如果字典等于 K，则更改字典值的Python程序

给定一个字典，如果它等于 K，就改变它的值。

Input : test_dict = {“Gfg”: 4, “is”: 8, “best”: 10, “for”: 8, “geeks”: 19}, K = 8, repl_val = 25 
Output : {‘Gfg’: 4, ‘is’: 25, ‘best’: 10, ‘for’: 25, ‘geeks’: 19} 
Explanation : All values with 8 converted to 25.

Input : test_dict = {“Gfg”: 6, “is”: 8, “best”: 10, “for”: 8, “geeks”: 19}, K = 6, repl_val = 25 
Output : {‘Gfg’: 25, ‘is’: 8, ‘best’: 10, ‘for’: 8, ‘geeks’: 19} 
Explanation : All values with 6 converted to 25. 

方法#1：使用循环

这是可以执行此任务的粗暴方式。在这里，我们迭代字典的所有键和值，如果找到匹配项，则执行所需的转换。

Python3

# Python3 code to demonstrate working of 
# Change value if value equals K in dictionary
# Using loop
  
# initializing dictionary
test_dict = {"Gfg": 4, "is": 8, "best": 10, "for": 8, "geeks": 19}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# initializing K  
K = 8
  
# initializing repl_val 
repl_val = 20
  
# iterating dictionary
for key, val in test_dict.items():
      
    # checking for required value
    if val == K:
        test_dict[key] = repl_val
  
# printing result 
print("The dictionary after values replacement : " + str(test_dict))

输出

The original dictionary is : {‘Gfg’: 4, ‘is’: 8, ‘best’: 10, ‘for’: 8, ‘geeks’: 19}
The dictionary after values replacement : {‘Gfg’: 4, ‘is’: 20, ‘best’: 10, ‘for’: 20, ‘geeks’: 19}

方法#2：使用字典理解

这是解决此问题的一种单行替代方法。在这种情况下，我们迭代并分配创建一个新字典，而不是像上面的方法那样进行就地替换。

蟒蛇3

# Python3 code to demonstrate working of 
# Change value if value equals K in dictionary
# Using dictionary comprehension
  
# initializing dictionary
test_dict = {"Gfg": 4, "is": 8, "best": 10, "for": 8, "geeks": 19}
  
# printing original dictionary
print("The original dictionary is : " + str(test_dict))
  
# initializing K  
K = 8
  
# initializing repl_val 
repl_val = 20
  
# one-liner to solve for dictionary
res = {key : repl_val if val == K else val for key, val in test_dict.items()}
  
# printing result 
print("The dictionary after values replacement : " + str(res))

输出

The original dictionary is : {‘Gfg’: 4, ‘is’: 8, ‘best’: 10, ‘for’: 8, ‘geeks’: 19}
The dictionary after values replacement : {‘Gfg’: 4, ‘is’: 20, ‘best’: 10, ‘for’: 20, ‘geeks’: 19}