在对象列表中查找属性值

Question

我有一个User的列表，我尝试根据id属性返回其中一个。

from pydantic import BaseModel,ValidationError
import json
class User(BaseModel):
id: int
name: str
age: int
class Data():
def __init__(self, jsonfile : str) :
self.users_list= []
with open(jsonfile) as f:
users = json.load(f)
for u in users :
try :
self.users_list.append(User(**u))
except ValidationError as e:
print(e.json())  

def get_user(self,id : int) -> User :
if self.users_list.index(id) : # How to search in my list of User for a specific id ?
return self.users_list.index(id)
else :
return None

我可以遍历User的整个列表并检查它们的id属性，但我想知道它们是否比

这样的东西更干净。

for u in self.users_list : 
if u.id == id :
return u

Answer 1

如果你想要最快的搜索时间，我建议使用字典，键是用户的id。

我做了一个python测试文件来测试python中不同的数据结构，以找到最快的解决方案。

以下是我的研究结果，以毫秒为单位:

List Append Time: 0.8620707350000001

字典追加时间:1.2875515819999999

设置追加时间:1.325187916

List Find User Time: 0.0658235330000001

字典查找用户时间:2.4221999999962662e-05

设置查找用户时间:0.10515519500000003

从我的测试中可以看出，字典比列表或集合快很多。

import time
class Counter:
_start = float
def __init__(self):
self.start_time()
def start_time(self):
self._start = time.perf_counter()
return self._start
@property
def time_elapsed(self):
time_elapsed = time.perf_counter() - self._start
self.start_time()
return time_elapsed

class User:
id: int
def __init__(self, user_id):
self.id = user_id
def __eq__(self, other):
return self.id == other
def __hash__(self):
return hash(self.id + id(self))
user_dict = {}
user_set = set()
users = []

counter = Counter()
for i in range(0, 1000000):
user = User(i)
users.append(user)
print('List Append Time: ', counter.time_elapsed)
for i in range(0, 1000000):
user = User(i)
user_dict[str(user.id)] = user
print('Dict Append Time: ', counter.time_elapsed)
for i in range(0, 1000000):
user = User(i)
user_set.add(user)
print('Set Append Time: ', counter.time_elapsed)

for user in users:
if user == 500000:
break
print('List Find User Time: ', counter.time_elapsed)
found_user = user_dict['500000']
print('Dict Find User Time: ', counter.time_elapsed)
for user in user_set:
if user == 500000:
break
print('Set Find User Time: ', counter.time_elapsed)