字典列表的返回值

Question

我有以下字典列表:

voting_data = [ {"county":"Arapahoe", "registered_voters": 422829}, {"county":"Denver", "registered_voters": 463353}, {"county":"Jefferson", "registered_voters": 432438}]

我需要创建一个for循环，当执行时，将产生以下句子:

阿拉帕霍县有422,829名登记选民;(以此类推)。

我已经被困了一整天，并尝试了不同的循环/变量。我不明白这是怎么回事。我知道我正在寻找检索每个项目的索引值(因此，对于" country "; "Arapahoe"我想找回"阿拉帕霍"。和"registered_voters": 422829， "422829"

最近，我想到了:

for counties_dict in voting_data:
for i in counties_dict.values("county") and j in counties_dict.values("registered_voters"):
print(f" {i} county has {j:,} registered voters")

Answer 1

不需要嵌套循环。您需要遍历列表，并访问字典的每个属性:

for vd in voting_data:
print(f'{vd["county"]} has {vd["registered_voters"]} registered voters')

Answer 2

您可以对dict.get()执行此操作以获取特定键的值。

for d in voting_data:
county = d.get('county')
voters = '{:,}'.format(d.get('registered_voters'))
print(f'{county} county has {voters} registered voters.')

Arapahoe county has 422,829 registered voters.
Denver county has 463,353 registered voters.
Jefferson county has 432,438 registered voters.    

注意:'{:,}'.format(100000)的结果是将数字格式化为100,000，并返回一个字符串，该字符串可以以您正在寻找的格式打印。

---

理解嵌套数据结构的行为是很重要的。您可以使用for-loop

迭代对象列表

for item in list:
print(item)

在本例中，项是字典。为了访问字典(键、值对)，您可以直接从对应的键访问值。

d = {'k1':'v1', 
'k2':'v2'}
>>> d['k1']
v1
#OR
>>> d.get('k1')
v1

如果你想迭代字典(键和值对)，那么你需要一个额外的for循环.

for k,v in d.items():
print(k, v)

(k1,v1)
(k2,v2)

希望这能澄清为什么你不需要嵌套循环。由于您有一个字典列表，因此可以遍历该列表，然后使用其特定键(在本例中是county和registered_voters)访问每个字典

Answer 3

类似如下(1 line)

voting_data = [ {"county":"Arapahoe", "registered_voters": 422829}, {"county":"Denver", "registered_voters": 463353}, {"county":"Jefferson", "registered_voters": 432438}]
output = [f'{x["county"]} County has {x["registered_voters"]:,} registered voters' for x in voting_data]
print(output)

输出

['Arapahoe County has 422,829 registered voters', 'Denver County has 463,353 registered voters', 'Jefferson County has 432,438 registered voters']