CODEWITHSUNDEEP
pythonlistflatten
Horai Nuri
Horai Nuri

Reputation: 5578

How to flatten mixed dimensional array into a two dimensional list?

I know there are many posts on how I can flatten a two-dimensional list but this one is a bit different because it's a mix of two dimensional and three-dimensional list :

items = [[255, 204, 204], ..., [255, 179, 179], [[250, 250, 250], ..., [220, 220, 220]]]

I'd like this list to be two dimentional only :

items = [[255, 204, 204], ..., [255, 179, 179], [250, 250, 250], ..., [220, 220, 220]]

I tried to use list comprehension but it doesn't flatten the list correctly :

flat_list = [item for items in l for item in items]

What would be the best way of flattening mixed dimensional array into a two-dimensional one?

Upvotes: 3

Views: 835

Answers (4)

englealuze
englealuze

Reputation: 1663

def tree2matrix(T):
  if T == []:
    return []
  elif type(T) is not list:
    return [[T]]
  elif type(T[0]) is not list:
    return [T]
  else:
    return tree2matrix(T[0]) + tree2matrix(T[1:])

X = [[255, 204, 204], [255, 179, 179], [['250, 250, 250'], ['220, 220, 220']]]
print(tree2matrix(X))

Upvotes: 0

Eugene Yarmash
Eugene Yarmash

Reputation: 150081

You can use a recursive function:

def flatten(items):
    for item in items:
        if isinstance(item[0], list):
            yield from flatten(item)
        else:
            yield item

Demo:

>>> items = [[255, 204, 204], [255, 179, 179], [['250, 250, 250'], ['220, 220, 220']]]
>>> list(flatten(items))
[[255, 204, 204], [255, 179, 179], ['250, 250, 250'], ['220, 220, 220']]

Upvotes: 3

javidcf
javidcf

Reputation: 59731

from itertools import chain

items = [[255, 204, 204], [255, 179, 179], [['250, 250, 250'], ['220, 220, 220']]]

flat_list = list(chain.from_iterable(lst if isinstance(lst[0], list) else [lst] for lst in items))

print(flat_list)
>>> [[255, 204, 204], [255, 179, 179], ['250, 250, 250'], ['220, 220, 220']]

Upvotes: 1

GuangshengZuo
GuangshengZuo

Reputation: 4687

old_list = [[255, 204, 204], [255, 179, 179], [['250, 250, 250'], ['220, 220, 220']]]                                                                                                         
new_list = []  
for i in old_list:
    if isinstance(i[0], list):
        for j in i:
            new_list.append(j)
    else:
        new_list.append(i)
print new_list

The output is:

[[255, 204, 204], [255, 179, 179], ['250, 250, 250'], ['220, 220, 220']]

Upvotes: 5

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