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pythontuples
Engo
Engo

Reputation: 969

How to get 2nd elements from tuples in Python?

I would like to have an array with all 2nd elements for which the first element is equal to 'tuple1elem1'. How can I do this efficiently? I have around 500 tuples.

Tuples:

(('tuple1elem1', 'tuple1elem2'), ('tuple2elem1', 'tuple2elem2'), ('tuple3elem1', 'tuple3elem2'))

What I would like to have:

array = ['tuple1elem2']

Upvotes: 1

Views: 17433

Answers (3)

Yi Xiang Chong
Yi Xiang Chong

Reputation: 764

There is a fast way to get and add only 2nd elements from list of tuples:

import numpy as np 

tuples_list = [(0, 10), (0, 20), (0, 30)]
fast_tuples_add = np.array(tuples_list) + (0, 9) # fast tuples add

fast_tuples_add
array([[ 0, 19],[ 0, 29], [ 0, 39]])

Hope this helps

Upvotes: 0

Christian König
Christian König

Reputation: 3570

You access elements from a tuple mostly the same way as elements of a list. You could for example unpack them:

>>> bigtuple = (('tuple1elem1', 'tuple1elem2'), ('tuple2elem1', 'tuple2elem2'), ('tuple3elem1', 'tuple3elem2'))
>>> array = [ele2 for ele1, ele2 in bigtuple if ele1 == "tuple1elem1"]
['tuple1elem2']

Upvotes: 1

merlin2011
merlin2011

Reputation: 75545

Use a list comprehension with a filter.

myList = [...]
output = [x[1] for x in myList if x[0] == 'tuple1elem1']

Upvotes: 7

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