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pythonlist
Jesh Kundem
Jesh Kundem

Reputation: 974

Three different lists into one list

I have three lists

a = ['abc', 'def', 'ghi']
b = ['123', '456', '789']
c = ['mar23', 'feb223', 'jan12']

How can I make this as follows: 

d = ['abc 123 mar23', 'def 456 feb223', 'ghi 789 jan12']

presently I am doing a for loop and doing index based concatenation. There should be an elegant way. Especially the space between them is causing the challenge. I am not looking for a dictionary.

Upvotes: 1

Views: 116

Answers (4)

Code Pope
Code Pope

Reputation: 5459

You can also use list comprehension:

d = [f'{a[i]} {b[i]} {c[i]}' for i,x in enumerate(a)]

Output:

['abc 123 mar23', 'def 456 feb223', 'ghi 789 jan12']

As in the accepted answer it is claimed that zip is faster than loop, I have made an extensive evaluation of both of them. The results show that if for smaller lists loop performs faster, but as the number of the elements increase zip outperforms. Here some graphs:

1. Amount of indices in the interval [4,64]: enter image description here

2. Amount of indices in the interval [64,4194304]: enter image description here

Upvotes: 0

r.ook
r.ook

Reputation: 13888

Use zip and list comprehension:

[' '.join(z) for z in zip(a, b, c)]

Result:

['abc 123 mar23', 'def 456 feb223', 'ghi 789 jan12']

Using index based vs zip runtime (n=1000000):

with index: 5.751067761
with zip:   4.115390091

Upvotes: 4

Soban
Soban

Reputation: 434

Use the Zip() function simply like this:

a = ['abc', 'def', 'ghi']
b = ['123', '456', '789']
c = ['mar23', 'feb223', 'jan12']

d = zip(a, b, c)

print(tuple(d))

Let me explain what is happening: We are first declaring 3 variables. Then, in order to join them together, we have a function zip() in Python which zips(or combines) the lists. So once we zip(a, b, c), we simply combine these 3 variables as a tuple while printing d(which contains the zipped items).

Hope it helps

Upvotes: 1

notablytipsy
notablytipsy

Reputation: 387

What you want is Python's zip

In [1]: a = ['abc', 'def', 'ghi'] 
   ...: b = ['123', '456', '789'] 
   ...: c = ['mar23', 'feb223', 'jan12']                                                                      
In [2]: [' '.join(t) for t in zip(a, b, c)]                                                                   
Out[2]: ['abc 123 mar23', 'def 456 feb223', 'ghi 789 jan12']

Upvotes: 1

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