l =[[1,2,3],[4,5],[6,7],[8,9,10,11]]
np.array(l).flatten().tolist()
D:\Anaconda3\lib\site-packages\ipykernel_launcher.py:2: VisibleDeprecationWarning: Creating an ndarray from ragged nested sequences (which is a list-or-tuple of lists-or-tuples-or ndarrays with different lengths or shapes) is deprecated. If you meant to do this, you must specify 'dtype=object' when creating the ndarray
defflatten(items, result=[]):for item in items:ifisinstance(item,list):
flatten(item, result)else:
result.append(item)
result =[]
flatten(l, result)
result
from collections import deque
stack = deque(l)
result =[]whilelen(stack)!=0:
item = stack.popleft()ifisinstance(item,list):for e inreversed(item):
stack.appendleft(e)else:
result.append(item)
result
from collections import deque
stack = l.copy()
result = deque()whilelen(stack)!=0:
item = stack.pop()ifisinstance(item,list):for e in item:
stack.append(e)else:
result.appendleft(item)
result =list(result)
result