donnemartin/interactive-coding-challenges · error · TypeError

array cannot be None or empty

Error message

array cannot be None or empty

What it means

Bits.new_int raises TypeError('array cannot be None or empty') because the algorithm maps input integers into a BitArray bit vector and then scans for the first unset bit; with no input there is nothing to map and the result would be meaningless. The 'not array' check rejects both None and empty lists.

Solutions

  1. Verify the array is populated before calling new_int; skip the call for empty inputs
  2. Check the upstream producer of the array (loop/file read) to see why it yielded no items
  3. If an empty array legitimately means 'answer is 0', handle that case in the caller instead of calling new_int

Example fix

// before
index = Bits().new_int(array, max_size)  # array may be []

// after
index = Bits().new_int(array, max_size) if array else 0
Defensive patterns

Strategy: validation

Validate before calling

if not array:
    # nothing to map; first free index is 0 by convention
    return 0
index = Bits().new_int(array, max_size)

Type guard

def has_items(x):
    return isinstance(x, list) and len(x) > 0

Try / catch

try:
    index = bits.new_int(array, max_size)
except TypeError:
    index = 0  # empty/None input treated as answer 0

Prevention

When it happens

Trigger: Calling Bits().new_int(None, max_size) or Bits().new_int([], max_size). Also triggered when max_size is omitted/misused so the array argument ends up empty.

Common situations: Feeding an empty result set from a previous computation into the missing-integer finder; optional function parameters defaulting to None; test harnesses checking boundary conditions.

Related errors

AI-assisted analysis of donnemartin/interactive-coding-challenges@358f2cc604 (2026-08-28). Data as JSON: /api/errors/7fb711d37b073a5b. Report an issue: GitHub.

Appendix: source

Thrown at sorting_searching/new_int/new_int_solution.ipynb:110

   "metadata": {},
   "source": [
    "## Code"
   ]
  },
  {
   "cell_type": "code",
   "execution_count": 1,
   "metadata": {},
   "outputs": [],
   "source": [
    "from bitstring import BitArray  # Run pip install bitstring\n",
    "\n",
    "\n",
    "class Bits(object):\n",
    "\n",
    "    def new_int(self, array, max_size):\n",
    "        if not array:\n",
    "            raise TypeError('array cannot be None or empty')\n",
    "        bit_vector = BitArray(max_size)\n",
    "        for item in array:\n",
    "            bit_vector[item] = True\n",
    "        for index, item in enumerate(bit_vector):\n",
    "            if not item:\n",
    "                return index\n",
    "        return None"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit Test"
   ]
  },
  {
   "cell_type": "code",

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