CODEWITHSUNDEEP
pythonlisttuples
user1413824
user1413824

Reputation: 669

python - get list of tuples first index?

What's the most compact way to return the following:

Given a list of tuples, return a list consisting of the tuples first (or second, doesn't matter) elements.

For:

[(1,'one'),(2,'two'),(3,'three')]

returned list would be

[1,2,3]

Upvotes: 38

Views: 39216

Answers (5)

Shameem
Shameem

Reputation: 2814

Try this.

>>> list(map(lambda x: x[0], my_list))

Upvotes: 3

SuperNova
SuperNova

Reputation: 27466

You can try this too..

dict(my_list).keys()

Upvotes: -2

fraxel
fraxel

Reputation: 35269

>>> mylist = [(1,'one'),(2,'two'),(3,'three')]
>>> [j for i,j in mylist]
['one', 'two', 'three']
>>> [i for i,j in mylist]
[1, 2, 3]

This is using a list comprehension (have a look at this link). So it iterates through the elements in mylist, setting i and j to the two elements in the tuple, in turn. It is effectively equivalent to:

>>> newlist = []
>>> for i, j in mylist:
...     newlist.append(i)
... 
>>> newlist
[1, 2, 3]

Upvotes: 14

gsagrawal
gsagrawal

Reputation: 3020

use zip if you need both 

>>> r=(1,'one'),(2,'two'),(3,'three')
>>> zip(*r)
[(1, 2, 3), ('one', 'two', 'three')]

Upvotes: 53

Tim Pietzcker
Tim Pietzcker

Reputation: 336128

>>> tl = [(1,'one'),(2,'two'),(3,'three')]
>>> [item[0] for item in tl]
[1, 2, 3]

Upvotes: 42

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