Python: Flatten List Of Lists Of Lists

I know this has been asked before but I don't see any solutions for when there is a list of the type: original_list = [[1,2], [3], [4,5,[6]]] Tried this method: def flatten(list):

Solution 1:

Something along these lines?

In [6]: original_list = [[1,2], [3], [4,5,[6]]]                                                                                                                         

In [7]: def flatten(potential_list): 
   ...:     new_list = [] 
   ...:     for e in potential_list: 
   ...:         if isinstance(e, list): 
   ...:             new_list.extend(flatten(e)) 
   ...:         else: 
   ...:             new_list.append(e) 
   ...:     return new_list 
   ...:                                                                                                                                                                 

In [8]: flatten(original_list)                                                                                                                                          
Out[8]: [1, 2, 3, 4, 5, 6]

Solution 2:

If you have nested-nested lists, the best way to flatten is using generator function

original_list = [[1,2], [3], [4,5,[6]]]

def flatten(l):
    for i in l:
        if isinstance(i,list):
            yield from flatten(i)
        else:
            yield i

list(flatten(original_list))
#[1, 2, 3, 4, 5, 6]

Solution 3:

You can use Collections.Iterable:

In [2810]: def flatten(x): 
      ...:     ifisinstance(x, collections.Iterable): 
      ...:         return [a for i in x for a in flatten(i)] 
      ...:     else: 
      ...:         return [x] 
      ...: 

In [2811]: flatten(original_list)
Out[2811]: [1, 2, 3, 4, 5, 6]

OR brute force like this:

In [2803]:flat_list= [] 
      ...:for sublist in original_list:...:for item in sublist:...:ifisinstance(item,list):...:for sub_item in item:...:flat_list.append(sub_item)...:else:...:flat_list.append(item)In [2804]:flat_listOut[2804]: [1, 2, 3, 4, 5, 6]

Solution 4:

Here's a recursive solution:

defrecursive_flatten(lst, retlist = []):
    for item in lst:
        iftype(item) isint:
            retlist.append(item)
        else:
            recursive_flatten(item, retlist)
    return(retlist)