How to remove all unnecessary arrays in nd array

问题

I have a nd python array (not a numpy array), and it looks something like this

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

I'd like to be able to remove all the unnecessary arrays so that I end up with

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

And I wrote a function to handle this

def remove_unnecessary(array:list) -> list:
    while True:
        try:
            array = *array
        except TypeError:
            return array

However this doesn't work, and that's mainly due to my lack of knowledge on using starred expressions to unwrap lists. Does anyone have an idea on how I could fix this or how I could better use * in this function?

回答1:

You can just iterate until you don't reach the inner elements. Example:

>>> def remove_unnecessary(l):
...     while len(l) == 1 and isinstance(l[0], list):
...             l=l[0]
...     return l
... 
>>> remove_unnecessary([[[1,2,3], [4,5,6]]])
[[1, 2, 3], [4, 5, 6]]
>>> remove_unnecessary([[[[[1,2,3], [4,5,6]]]]])
[[1, 2, 3], [4, 5, 6]]
>>> remove_unnecessary([1])
[1]
>>> remove_unnecessary([[1]])
[1]

回答2:

You can try this:

>>> import numpy as np
>>> l = [[[1,2,3]]]
>>> list(np.array(l).flatten())
[1, 2, 3]

回答3:

I wrote a recursive function for this. Let me know if this does the job for you.

Code

def list_flatten(example: list) -> list:
    try:
        if example:
            if len(example) > 1:
                return example
            elif len(example) == 1 and len(example[0]) != 1:
                return [elem for element in example for elem in element]
            elif len(example) == 1 and len(example[0]) == 1:
                return list_flatten(example[0])
        else:
            return "List empty"
    except TypeError:
        return example

Sample Inputs

example_list = [[[[[1,2,3], [4,5,6], [1]]]]]
example_list_test = [1, 3, 4, 5, 6, 7]
empty_example = []

Outputs

list_flatten(example_list) gives:
[[1, 2, 3], [4, 5, 6], [1]]

list_flatten(example_list_test) gives:
[1, 3, 4, 5, 6, 7]

list_flatten(empty_example) gives:
'List empty'

来源：https://stackoverflow.com/questions/60128295/how-to-remove-all-unnecessary-arrays-in-nd-array

标签

python

python-3.x

multidimensional-array