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pythonstringlist
Robin
Robin

Reputation: 1

a function that chages the structure of a python list

I plan to write a python function that can change the structure of a list. The input is:

list=[['A B C','D E F'],['1 2 3 ', '4 5 6 ']]

The output is:

list=[['A','B','C','D','E','F'],['1','2','3','4','5','6']]

I know I need the split() and append(). The confusing part is the loops. Thanks so much!!

Upvotes: 0

Views: 72

Answers (4)

Bi Rico
Bi Rico

Reputation: 25833

Sometimes it's best not to over think it. Lets start with just one piece of your problem, ['A B C','D E F'] . You want to split each string, and put parts into a result list. Let's start by writing that function. You've correctly stated that this can be done using split/append, but lists also happen to have an extend method which will save you a few lines of code.

def as_char(seq):
    result = []
    for item in seq:
        result.extend(item.split())
    return result

Now you want to apply that function to every list in your input. For that you can use map for a list comprehension.

sample_input = [['A B C','D E F'],['1 2 3 ', '4 5 6 ']]
output = map(as_char, sample_input)
# or
output = [as_char(item) for item in sample_input]

Upvotes: 3

Padraic Cunningham
Padraic Cunningham

Reputation: 180481

Join your subelements making sure to leave a space when joining then split on whitespace to split into individual elements and remove any trailing whitespace.

print([ " ".join(sub).split() for sub in l])
[['A', 'B', 'C', 'D', 'E', 'F'], ['1', '2', '3', '4', '5', '6']]

If you only have two subelements unpack and split using str.format to allow a space between for splitting:

print([ "{} {}".format(a,b).split() for a,b in l ])

[['A', 'B', 'C', 'D', 'E', 'F'], ['1', '2', '3', '4', '5', '6']]

If you are using list as a variable name then don't as you will be shadowing the builtin list which often leads to more questions on SO...

Upvotes: 2

Malik Brahimi
Malik Brahimi

Reputation: 16711

Use the join method to join the contain elements in the nested lists. Then split at the spaces.

my_list = [['A B C', 'D E F'], ['1 2 3 ', '4 5 6']]
my_list = [' '.join(i).split() for i in my_list]

Upvotes: 4

Hackaholic
Hackaholic

Reputation: 19753

How about this:

>>> my_list = [['A B C','D E F'],['1 2 3 ', '4 5 6 ']]
>>> map(lambda x:x.split(), map(" ".join, my_list))
[['A', 'B', 'C', 'D', 'E', 'F'], ['1', '2', '3', '4', '5', '6']]

Upvotes: 0

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