Python: how to paste a list into another list

Question

Help me please with this problem: I have a list containing numbers and lists kind of:

list = [1,2,[3,4,5],6,7,[8,9]]

What I want to get is a list of just numbers (mergin included lists in parent list): Example:

new_list = [1,2,3,4,5,6,7,8,9]

Answer 1

Using recursion and collections.Iterable:

>>> from collections import Iterable
>>> def flat(lst):
...     for parent in lst:
...         if not isinstance(parent, Iterable):
...             yield parent
...         else:
...             for child in flat(parent):
...                 yield child
...
>>> list(flat(t))
[1, 2, 3, 4, 5, 6, 7, 8, 9]

Just remember to not name lists after their own type :).

Answer 2

I personally use this method :

This is a functional version of recursive flatten which handles both tuples and lists, and lets you throw in any mix of positional arguments. Returns a generator which produces the entire sequence in order, arg by arg:

flatten = lambda *n: (e for a in n
    for e in (flatten(*a) if isinstance(a, (tuple, list)) else (a,)))

Usage:

l1 = ['a', ['b', ('c', 'd')]]
l2 = [0, 1, (2, 3), [[4, 5, (6, 7, (8,), [9]), 10]], (11,)]
print list(flatten(l1, -2, -1, l2))
['a', 'b', 'c', 'd', -2, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11]

This works fine with both python 3.x and python 2.x

Here is a regex solution for the same ..

 import re

 def Flatten(TheList):
   a = str(TheList)
   b,crap = re.subn(r'[\[,\]]', ' ', a)
   c = b.split()
   d = [int(x) for x in c]

   return(d)