Python Insert a list into a list

Question

I have a list like this:

a = ["a","b","c","d","e"]

How do I insert a word to the end of each item in the list and make them as list itself?

Expected output:

a = [("a","TEST"),("b","TEST"),("c","TEST"),("d","TEST"),("e","TEST")]

I have tried a lot of ways but no luck getting that.

Ajax1234 · Accepted Answer · 2017-09-13 14:43:39Z

9

Create a tuple with the item and the desired word:

word = "TEST"
a = ["a","b","c","d","e"]
new_a = [(i, word) for i in a]

Output:

[('a', 'TEST'), ('b', 'TEST'), ('c', 'TEST'), ('d', 'TEST'), ('e', 'TEST')]

Alternatively, using map:

new_a = list(map(lambda x: (x, "TEST"), a))

edited Sep 13, 2017 at 14:43

answered Sep 13, 2017 at 14:38

Ajax1234

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3 Comments

Kenny C Over a year ago

Sorry for bothering again, is there any way to eliminate the space between 'a', and 'TEST'? I need to unpack it for the classifier function

Ajax1234 Over a year ago

@KennyC the space is natural Python syntax. ('a', 'TEST') is equivalent to ("a","TEST").

syntacticmarmalade Over a year ago

Don't use map. List comprehensions are more pythonic

ettanany · Accepted Answer · 2017-09-13 14:54:22Z

2

Another way is using zip_longest from itertools module like below (but the solution to go with should be Ajax1234's one using tuple in a list comprehension):

from itertools import zip_longest

l = ['a', 'b', 'c', 'd', 'e']
res = list(zip_longest(l, ['TEST'], fillvalue='TEST'))

Output:

>>> res
[('a', 'TEST'), ('b', 'TEST'), ('c', 'TEST'), ('d', 'TEST'), ('e', 'TEST')]

edited Sep 13, 2017 at 14:54

answered Sep 13, 2017 at 14:43

ettanany

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Comments

Don · Accepted Answer · 2017-09-13 14:39:36Z

1

You can use zip:

a = ["a","b","c","d","e"]
new_a = zip(a, ["TEST"] * len(a))

output:

[('a', 'TEST'), ('b', 'TEST'), ('c', 'TEST'), ('d', 'TEST'), ('e', 'TEST')]

answered Sep 13, 2017 at 14:39

Don

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Comments

am2 · Accepted Answer · 2017-09-13 14:43:07Z

1

Not very hip, but similar to other common languages:

a = ["a","b","c","d","e"]
b = []

for x in a:
    b.append ( (x, 'TEST'))

a = b

print a

answered Sep 13, 2017 at 14:43

am2

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1 Comment

Abe Over a year ago

maybe add two lists inst the solution

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