donnemartin/interactive-coding-challenges · error · ValueError

Invalid event type

Error message

Invalid event type

What it means

Raised inside Solution.find_busiest_period while iterating the sorted event list: an interval's event_type is neither EventType.ENTER nor EventType.EXIT. The visitor-count arithmetic depends on the event direction, so unknown types are rejected mid-loop with ValueError.

Source

Thrown at online_judges/busiest_period/busiest_period_solution.ipynb:181

   "source": [
    "class Solution(object):\n",
    "\n",
    "    def find_busiest_period(self, data):\n",
    "        if data is None:\n",
    "            raise TypeError('data cannot be None')\n",
    "        if not data:\n",
    "            return None\n",
    "        data.sort()\n",
    "        max_period = Period(0, 0)\n",
    "        max_people = 0\n",
    "        curr_people = 0\n",
    "        for index, interval in enumerate(data):\n",
    "            if interval.event_type == EventType.ENTER:\n",
    "                curr_people += interval.num_people\n",
    "            elif interval.event_type == EventType.EXIT:\n",
    "                curr_people -= interval.num_people\n",
    "            else:\n",
    "                raise ValueError('Invalid event type')\n",
    "            if (index < len(data) - 1 and \n",
    "                    data[index].timestamp == data[index + 1].timestamp):\n",
    "                continue\n",
    "            if curr_people > max_people:\n",
    "                max_people = curr_people\n",
    "                max_period.start = data[index].timestamp\n",
    "                if index < len(data) - 1:\n",
    "                    max_period.end = data[index + 1].timestamp\n",
    "                else:\n",
    "                    max_period.end = data[index].timestamp\n",
    "        return max_period"
   ]
  },
  {
   "cell_type": "markdown",
   "metadata": {},
   "source": [
    "## Unit Test"

View on GitHub (pinned to 358f2cc604)

Solutions

1. Map event types to the enum when building data: EventType.ENTER for arrivals, EventType.EXIT for departures
2. Validate event_type in your Interval factory/deserializer before calling find_busiest_period
3. Check for enum renames if code worked before a version change

Example fix

# before
Interval(1, 10, 1)  # raw int not in EventType -> ValueError

# after
Interval(1, 10, EventType.ENTER)

valid = {EventType.ENTER, EventType.EXIT}
for iv in data:
    if iv.event_type not in valid: raise ValueError('bad event_type')
solution.find_busiest_period(data)

def is_valid_event(t): return t in (EventType.ENTER, EventType.EXIT)

try:
    solution.find_busiest_period(data)
except ValueError as e:
    # drop or re-map invalid events, then retry
    data = [iv for iv in data if is_valid_event(iv.event_type)]
    solution.find_busiest_period(data)

When it happens

Trigger: Calling find_busiest_period with an Interval whose event_type is e.g. 2, 'enter', or a typo'd enum member — anything outside {EventType.ENTER, EventType.EXIT}.

Common situations: Constructing test data with raw ints/strings instead of enum members; enum refactors that renamed or added members; deserializing events from JSON where the type field wasn't mapped to the enum.

Understand the failure class

Background: Invalid enum value errors: "Unknown type", "Invalid scope", "must be one of" — when a string is not on the library's allowed list — this error's family across 23 libraries.

Related errors

• data cannot be None
• num cannot be None
• max_num cannot be None
• val cannot be None
• n cannot be None

AI-assisted analysis of donnemartin/interactive-coding-challenges@358f2cc604 (2026-08-28). Data as JSON: /api/errors/0a7eb3461fbb14d7. Report an issue: GitHub.