how to convert two list into nested list in python code example

Example 1: convert 2 level nested list to one level list in python

>>> from collections import Iterable
>>> def flat(lst):
...     for parent in lst:
...         if not isinstance(i, Iterable):
...             yield parent
...         else:
...             for child in flat(parent):
...                 yield child
...
>>> list(flat(([1,[2,2,2],4]))
[1, 2, 2, 2, 4]

Example 2: how to make one list from nested list

>>> from collections import Iterable
def flatten(lis):
     for item in lis:
         if isinstance(item, Iterable) and not isinstance(item, str):
             for x in flatten(item):
                 yield x
         else:        
             yield item

>>> lis = [1,[2,2,2],4]
>>> list(flatten(lis))
[1, 2, 2, 2, 4]
>>> list(flatten([[1, 2, 3], [4, 5, 6], [7, 8, 9]]))
[1, 2, 3, 4, 5, 6, 7, 8, 9]