在Python中按属性获取对象列表中的索引
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Get index in the list of objects by attribute in Python
提问by sebaszw
I have list of objects with attribute id and I want to find index of object with specific id. I wrote something like this:
我有具有属性 id 的对象列表，我想找到具有特定 id 的对象索引。我写了这样的东西：
index = -1
for i in range(len(my_list)):
if my_list[i].id == 'specific_id'
index = i
break
but it doesn't look very well. Are there any better options?
但它看起来不太好。有没有更好的选择？
采纳答案by Abhishek
Assuming
假设
a = [1,2,3,4]
val = 3
Do
做
a.index(val) if val in a else -1
For multiple occurrence, as per Azam's comment below:
对于多次出现，根据下面 Azam 的评论：
[i if val == x else -1 for i,x in enumerate(a)]
Edit1:
For everyone commenting that its List of object, all you need is, access the id
Edit1：对于每个评论其对象列表的人，您只需要访问 id
[i if val == x.id else -1 for i,x in enumerate(a)]
回答by Daniel Roseman
You can use enumerate:
您可以使用enumerate：
for index, item in enumerate(my_list):
if item.id == 'specific_id':
break
回答by Joel Cornett
Use enumeratewhen you want both the values and indices in a forloop:
使用enumerate时，你在想这两个值和指数for环：
for index, item in enumerate(my_list):
if item.id == 'specific_id':
break
else:
index = -1
Or, as a generator expression:
或者，作为生成器表达式：
index = next((i for i, item in enumerate(my_list) if item.id == 'specific_id'), -1)
回答by chepner
Here's an alternative that doesn't use an (explicit) loop, with two different approaches to generating the list of 'id' values from the original list.
这是一个不使用（显式）循环的替代方法，有两种不同的方法可以从原始列表中生成“id”值列表。
try:
# index = map(operator.attrgetter('id'), my_list).index('specific_id')
index = [ x.id for x in my_list ].index('specific_id')
except ValueError:
index = -1
