Python-Coding-Challenge

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1

[Coding-Challenge-Python/Flatten-Array · GitHub]

Here is my solution for the Python3 Coding Challenge- Flatten possible multi-dimensional array
I included two possible ways to check is and element in an array is an array:

  1. type()
  2. isinstance()
def flatten_array(arr): # Write your code here flat_list = [] # Iterate through the outer list for element in arr: #if type(element) is list: if isinstance(element, list): # If the element is of type list, iterate through the sublist or inner list for item in element: flat_list.append(item) else: flat_list.append(element) return flat_list print(flatten_array([1, 2, [3, 4, 5], 6, [7, 8], 9])) print(flatten_array([[2], [8, 9, 10,], 5, 4, []] ))
3 Likes
2

Here’s a one-liner using the built-in collections and itertools modules.

import collections.abc
from itertools import chain


def flatten_array(arr):
    return list(chain.from_iterable(n if isinstance(n, collections.abc.Iterable) and
                                         not isinstance(n, str) else [n] for n in arr))


if __name__ == '__main__':
    print(flatten_array([1, 2, [3, 4, 5], 6, [7, 8], 9]))  # [1, 2, 3, 4, 5, 6, 7, 8, 9]
    print(flatten_array([[2], [8, 9, 10, ], 5, 4, []]))  # [2, 8, 9, 10, 5, 4]
3

Hello,

I got the correct output every time I passed an argument to my function, but I kept receiving the following error:

“‘<’ not supported between instances of ‘list’ and ‘int’”. Check your code and try again.

Anyone have an idea of what I am missing?

def flatten_array(arr): for i, element in enumerate(arr): if isinstance(element, list): arr.extend(element) arr.pop(i) return sorted(arr) print(flatten_array([[-1, -2, -3, 100], 1, 2, [11, 0, 3], 6, [7, 8], 9]))
5

fyi - As I continued completing the Python-Coding-Challenges I encountered notes from codecademy stating that the challenges should be completed without the use of imports, and itertools was specifically identified.

1 Like
6

Consider the slightly different argument,

print(flatten_array([[-1, -2, -3, 100], [1, 2], 2, [11, 0, 3], 6, [7, 8], 9]))

For the above, your code gives the error:

TypeError: ‘<’ not supported between instances of ‘int’ and ‘list’

For the above test case, not all the lists are being flattened. When you call sorted(arr), the sorted function can’t decide how to sort a mixture of integers and lists.

Try adding a print statement(s) as the first line of your loop for debugging purposes. It will help you see what is going on.

def flatten_array(arr):
    for i, element in enumerate(arr):
        print("Loop variable i:", i)
        print("Element being processed:", element)
        print("Array:", arr, "\n")
        if isinstance(element, list): 
            arr.extend(element)
            arr.pop(i)
    return sorted(arr)
7

the_list = [[1, 2], 3, 4, [ 5, 10, 20], 8]
enumerate is not necessary.neither is pop(), etc…

the flatten (method) function will return a single array (list) of each element and remove all the nested lists
this is the intent.
flattened_list = [1, 2, 3, 4, 5, 10, 20, 8] (because the_list elements will be appended to falttened_list by function)
enumerate will return a list of tuples like so:

[(0, 1), (1, 2), (2, 3), (3, 4), (4, 5), (5, 10), (6, 20), (7, 8)]
that is not a flattened list

I’m not sure this is the information you want.

8

Where is the error you receive?

I ran the code on the error you received and got the correct output.

[-3, -2, -1, 0, 1, 2, 3, 6, 7, 8, 9, 11, 100]

9

With which of the two arguments did you test your code?

flatten_array([[-1, -2, -3, 100], [1, 2], 2, [11, 0, 3], 6, [7, 8], 9])

# OR

flatten_array([[-1, -2, -3, 100], 1, 2, [11, 0, 3], 6, [7, 8], 9])