Reading first non-list value from the arbitrary nested list

Question

How to write a function which needs to access the first value which is not a list from an arbitray-deep nested list? Sometimes right syntax will be somelist[0], some other time somelist[0][0] etc. Is flattening of the whole list just to read the first one correct solution?

score 0 · Answer 1 · edited May 23 '17 at 11:57

0

This has been answered here.

Summarizing:

from itertools import chain
myList = [ [1, 2, 3], [5, 6], [], [114, 66, 55] ]
flatList = list( chain( *myList ) )

Output: [1, 2, 3, 5, 6, 114, 66, 55]

Then just access flatList[0] for the first element.

edited May 23 '17 at 11:57

Community

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answered May 08 '14 at 13:08

Tejas Pendse

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score 0 · Accepted Answer · answered May 08 '14 at 13:12

0

I would do something like

value = my_list[0]
if isinstance(value, list):
    value = value[0]

# use the value

answered May 08 '14 at 13:12

mpcabd

1,813
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score 0 · Answer 3 · answered May 08 '14 at 13:18

0

Try this:

def get_first_item(value):
    if isinstance(value, list):
        return get_first_item(value[0])
    return value

answered May 08 '14 at 13:18

fred.yu

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Reading first non-list value from the arbitrary nested list

3 Answers3