lol

def rec(arr):
    for i in range(len(arr)):
        if arr[i] == '_':
            arr[i] = 0
            rec(arr.copy())
            arr[i] = 1
            rec(arr.copy())
            break
        if i == len(arr) - 1:
            print(arr)

arr = [0, '_', '_', 1, '_']
rec(arr)