Python - how to split a string list into two?

Question

There is a list like:

list = ['AB', 'CD', 'EF', 'GH']

I would like to split this list like:

first =  ['A', 'C', 'E', 'G']
second = ['B', 'D', 'F', 'H']

Now I did like this :

for element in list:
    first.append(element[0])
    second.append(element[1])

Is it a good way? Actually, the length of list over 600,000.

You can just do first, second = zip(*l) (granted zip will return tuples, which you could then cast into a list. — Bahrom
– Bahrom, Commented Oct 17, 2017 at 20:33
Your way seems perfectly fine, to be honest. If you know for sure you always have two characters, you can do for c1, c2 in my_list: — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Oct 17, 2017 at 20:39
@Bahrom the thing I don't like about that approach is that the * splat operator actually materializes a tuple, so, if the number of arguments is large, this becomes increasingly inefficient. — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Oct 17, 2017 at 20:40
@Bahrom although, on my own initial tests it seems to beat out the naive approach by a good bit, I guess there's a major advantage to pushing the iteration out of the interpreter level... — juanpa.arrivillaga
– juanpa.arrivillaga, Commented Oct 17, 2017 at 20:52

Martijn Pieters · Accepted Answer · 2017-10-17 20:51:58Z

2

You can try this:

list = ['AB', 'CD', 'EF', 'GH']

first, second = zip(*list)
print(first)
print(second)

Output:

('A', 'C', 'E', 'G')
('B', 'D', 'F', 'H')

Martijn Pieters

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answered Oct 17, 2017 at 20:34

Ajax1234

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Comments

Chetan_Vasudevan · Accepted Answer · 2017-10-17 20:39:15Z

1

Looping through the list and appending to a pair of empty list can be done something like the below shown example.

 list = ['AB', 'CD', 'EF', 'GH']
 first=[]
 second=[]
 for f in list:
    first.append(f[0])
    second.append(f[1])
 print(first)
 print(second)

The output would be like

['A', 'C', 'E', 'G']

['B', 'D', 'F', 'H']

answered Oct 17, 2017 at 20:39

Chetan_Vasudevan

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How is your code different from what OP posted in the question?