CODEWITHSUNDEEP
pythonpython-3.x
Nour Galaby
Nour Galaby

Reputation: 11

Using comprehension lists for choosing items by index with duplicates

Trying to choose items from a list by another list of indices by looping over them and choosing them by index, but the result is missing duplicate items .

example.

X = [[1, 'a', 33], [2, 'a', 44], [3, 'bb', 56]] #sample data
indices = [1,1,1]        #index with duplicates
[ x[-1] for i,x in enumerate(X) if i in indices]

I expect 

[[2, 'a', 44], [2, 'a', 44], [2, 'a', 44]]

but I get 

[[2, 'a', 44]]

I tried normal loop instead of comprehnsion and it works. but doesnt work when I try to get part of the list inside. so I want

Upvotes: 1

Views: 28

Answers (2)

Don Cheeto
Don Cheeto

Reputation: 121

Try this 

 [mainL[x] for x in indices]

Output:

[[2, 'a', 44], [2, 'a', 44], [2, 'a', 44]]

Upvotes: 0

Netwave
Netwave

Reputation: 42746

You want to iterate indices in the comprehension and pick that element from X:

>>> X = [[1, 'a', 33], [2, 'a', 44], [3, 'bb', 56]]
>>> indices = [1,1,1]
>>> [X[i] for i in indices]
[[2, 'a', 44], [2, 'a', 44], [2, 'a', 44]]

In your case it do not work because you i will be 1 only once in the iteration with enumerate

Upvotes: 1

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