Python – 将频率字典转换为列表

有时，在使用Python字典时，我们可能会遇到需要根据字典的值构造列表的问题。此任务与查找频率相反，并且在日常编程和 Web 开发领域有应用。让我们讨论可以执行此任务的某些方式。

Input : test_dict = {‘gfg’ : 3, ‘ide’ : 2}
Output : [‘gfg’, ‘gfg’, ‘gfg’, ‘ide’, ‘ide’]

Input : test_dict = {‘practice’ : 1, ‘write’ : 2, ‘ide’ : 4}
Output : [‘practice’, ‘write’, ‘write’, ‘ide’, ‘ide’, ‘ide’, ‘ide’]

方法#1：使用循环
这是解决这个问题的粗暴方法。在此，我们迭代字典并提取频率并以该频率复制元素。

# Python3 code to demonstrate working of 
# Convert Frequency dictionary to list
# Using loop
  
# initializing dictionary
test_dict = {'gfg' : 4, 'is' : 2, 'best' : 5}
  
# printing original dictionary
print("The original dictionary : " + str(test_dict))
  
# Convert Frequency dictionary to list
# Using loop
res = []
for key in test_dict:
    for idx in range(test_dict[key]):
        res.append(key)
      
# printing result 
print("The resultant list : " + str(res)) 

输出 ：

The original dictionary : {‘is’: 2, ‘best’: 5, ‘gfg’: 4}
The resultant list : [‘is’, ‘is’, ‘best’, ‘best’, ‘best’, ‘best’, ‘best’, ‘gfg’, ‘gfg’, ‘gfg’, ‘gfg’]

方法#2：使用列表推导
该方法在工作方面与上述方法类似。这是上述方法的简写。

# Python3 code to demonstrate working of 
# Convert Frequency dictionary to list
# Using list comprehension
  
# initializing dictionary
test_dict = {'gfg' : 4, 'is' : 2, 'best' : 5}
  
# printing original dictionary
print("The original dictionary : " + str(test_dict))
  
# Convert Frequency dictionary to list
# Using list comprehension
res = [[key] * test_dict[key] for key in test_dict]
      
# printing result 
print("The resultant list : " + str(res)) 

输出 ：

The original dictionary : {‘is’: 2, ‘best’: 5, ‘gfg’: 4}
The resultant list : [‘is’, ‘is’, ‘best’, ‘best’, ‘best’, ‘best’, ‘best’, ‘gfg’, ‘gfg’, ‘gfg’, ‘gfg’]