> ## Documentation Index
> Fetch the complete documentation index at: https://leetcode-py.wisl.dev/llms.txt
> Use this file to discover all available pages before exploring further.

> ## Agent Instructions
> leetcode-py is a Python LeetCode practice environment generator with one CLI: lcpy. It is not a service or platform.
> Each problem is a directory under leetcode/ with README.md, solution.py, test_solution.py, helpers.py, and playground.ipynb. lcpy gen creates them from JSON templates bundled with the package.
> Examples are backed by tests; copy them verbatim.

# lcpy gen Error: Problem Not Found

> lcpy reports a problem number, name, or tag it cannot find. Check the catalog with lcpy list, use snake_case names, or upgrade the package.

```
Error: Problem number 42 not found
```

`lcpy gen` resolves numbers and tags against the JSON catalog bundled with
your installed version. The error means the number, name, or tag is not in
that catalog. A close cousin, reported as a warning during bulk runs:

```
Warning: JSON file not found for problem 'two-sum', skipping
```

That one means the name does not match a catalog entry, most often because
the name is spelled as a slug instead of snake\_case.

## Reproduce

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -n 42
# Error: Problem number 42 not found

lcpy gen -s two-sum
# Warning: JSON file not found for problem 'two-sum', skipping
# Completed: 0 successful, 1 failed
```

## Fix

* **Check what ships with your version**: run `lcpy list`, or `lcpy list -t <tag>` for one collection. Only listed problems can be generated.
* **With `-s`, spell the name exactly as the repo does, underscored**:
  `two_sum`, `valid_palindrome`. The hyphenated form (`two-sum`) is the
  LeetCode URL slug and matches nothing. Numbers via `-n` sidestep
  spelling entirely:

```bash theme={"theme":{"light":"github-light","dark":"github-dark"}}
lcpy gen -s two_sum
# ✅ Generated problem: two_sum
# Completed: 1 successful, 0 failed
```

* **Problem added to the repo after you installed**: upgrade the package,
  `pip install --upgrade leetcode-py-sdk`, then generate again.
* **Problem not in the catalog at all**: it has to be scraped and added
  first; see [Problem Creation](/contributing/problem-creation).

Not this error? Every fix lives on
[Troubleshooting](/troubleshooting).