python: convert “5,4,2,4,1,0” into [[5, 4], [2, 4], [1, 0]]

Question

Is there a \"straightforward\" way to convert a str containing numbers into a list of [x,y] ints?

# from: \'5,4,2,4,1,0,3,0,5,1,3,3,14,32,3,5\'
# to: [[5, 4         


        

Answer 1

First, use split to make a list of numbers (as in all of the other answers).

num_list = num_str.split(",")

Then, convert to integers:

num_list = [int(i) for i in num_list]

Then, use the itertools groupby recipe:

from itertools import izip_longest
def grouper(n, iterable, fillvalue=None):
   "grouper(3, 'ABCDEFG', 'x') --> ABC DEF Gxx"
   args = [iter(iterable)] * n
   return izip_longest(fillvalue=fillvalue, *args)

pair_list = grouper(2, num_list)

Of course, you can compress this into a single line if you're frugal:

pair_list = grouper(2, [int(i) for i in num_str.split(",")]

Answer 2

EDIT: @drewk cleaned this up to handle even or odd length lists:

>>> f = '5,4,2,4,1,0,3,0,5,1,3,3,14,32,3,5'
>>> li = [int(n) for n in f.split(',')]
>>> [li[i:i+2] for i in range(0, len(li), 2)]
[[5, 4], [2, 4], [1, 0], [3, 0], [5, 1], [3, 3], [14, 32], [3, 5], [7]]

Answer 3

#declare the string of numbers
str_nums = '5,4,2,4,1,0,3,0,5,1,3,3,14,32,3,5'

#zip two lists: the even elements with the odd elements, casting the strings to integers
zip([int(str_nums.split(',')[i]) for i in range(0,len(str_nums.split(',')),2)],[int(str_nums.split(',')[i]) for i in range(1,len(str_nums.split(',')),2)])

"""
Of course you would want to clean this up with some intermediate variables, but one liners like this is why I love Python :)
"""

Answer 4

>>> num_str = '5,4,2,4,1,0,3,0,5,1,3,3,4,3,3,5'
>>> inums = iter([int(x) for x in num_str.split(',')])
>>> [[x, inums.next()] for x in inums]
[[5, 4], [2, 4], [1, 0], [3, 0], [5, 1], [3, 3], [4, 3], [3, 5]]
>>>

Answer 5

One option:

>>> num_str = '5,4,2,4,1,0,3,0,5,1,3,3,4,3,3,5'
>>> l = num_str.split(',')
>>> zip(l[::2], l[1::2])
[('5', '4'), ('2', '4'), ('1', '0'), ('3', '0'), ('5', '1'), ('3', '3'), ('4', '3'), ('3', '5')]

Reference: str.split(), zip(), General information about sequence types and slicing

If you actually want integers, you could convert the list to integers first using map:

>>> l = map(int, num_str.split(','))

Explanation:

split creates a list of the single elements. The trick is the slicing: the syntax is list[start:end:step]. l[::2] will return every second element starting from the first one (so the first, third,...), whereas the second slice l[1::2] returns every second element from the second one (so the second, forth, ...).

Update: If you really want lists, you could use map again on the result list:

>>> xy_list = map(list, xy_list)

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Note that @Johnsyweb's answer is probably faster as it seems to not do any unnecessary iterations. But the actual difference depends of course on the size of the list.