python - 如何使用列表/字典理解在 Python 中获取唯一值

Question

我只需要从字典中的“city”字段中获取唯一值。我需要使用列表/字典理解来做到这一点。

people = [ dict ( city = "Liverpool" , name = "Adam" , age = 24 ),
{ "city" : "New York" , "name" : "Dario" , "age" : 12 },
{ "city" : "New York" , "name" : "Mario" , "age" : 45 },
{ "city" : "Chicago" , "name" : "Paolo" , "age" : 27 },
{ "city" : "Brighton" , "name" : "Sven" , "age" : 19 },
{ "city" : "Berlin" , "name" : "Frank" , "age" : 52 },
{ "city" : "Rome" , "name" : "Aleksander" , "age" : 33 }
{ "city" : "Rome" , "name" : "Adam," , "age" : 24 }]

我是这样用循环完成的:

unique_cities = []
for x in range(len(people)):
    y = people[x]
    cities = y.get('city')
    unique_cities.append(cities)
unique_cities = list(dict.fromkeys(unique_cities))
print(unique_cities)

但我之前没有处理过列表/字典理解。我只能像这样打印所有值:

for x in range(len(people)):
    y = people[x]
    dict_comp = {k:v for (k, v) in y.items()}
    print(dict_comp)

Answer 1

列表理解，并将其传递给集合。

set(person['city'] for person in people)

注意:实际上，这是一个生成器表达式，而不是列表理解，但在这种情况下，它们在大多数情况下是等价的