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Create Practice File (new_practice)

Status: Informational
Scope: Creating practice skeleton files in practices/ via scripts/new_practice.bat / scripts/new_practice.sh
Last Updated: January 4, 2026 15:11:06
Created: January 3, 2026 20:46:46

scripts/new_practice.bat / scripts/new_practice.sh are thin wrappers around CodeGen:

  • They run python -m codegen practice ...
  • They forward all arguments as-is
  • They return the same exit code as CodeGen

Source: scripts/new_practice.bat

When to use this

Use this command when you want to generate or refresh a practice file:

  • Output file location: practices/
  • Output filename format: <id:04d>_<slug>.py (example: 0023_merge_k_sorted_lists.py)

If the practice file already exists (and you are not using --dry-run), it will be backed up to:

  • practices/_history/<filename>.<YYYYMMDD_HHMMSS>.bak

Usage

Run from the repository root.

Windows

.\scripts\new_practice.bat <problem_id> [--all-solutions] [--dry-run]

Linux / macOS

./scripts/new_practice.sh <problem_id> [--all-solutions] [--dry-run]

Equivalent direct command (same behavior):

python -m codegen practice <problem_id> [--all-solutions] [--dry-run]

Parameters

Required

  • problem_id (int): LeetCode problem number (frontend id), e.g. 23

Optional flags

  • --all-solutions: If the reference solution contains multiple Solution classes, include all of them in the generated practice file.
  • Default behavior (without this flag): include only the single practice Solution.
  • --dry-run: Print generated content to stdout and do not write practices/<file>.py.
  • Important: in dry-run mode, no history backup is created.

What gets generated

CodeGen tries to generate the practice file using one of two strategies:

  • Reuse from an existing reference solution (preferred): if solutions/<id>_<slug>.py exists, CodeGen reuses its imports/helpers/codec infrastructure and only clears the practice implementation.
  • Generate a fresh skeleton: if no reference solution exists, CodeGen fetches problem metadata (slug/title) and generates a standard skeleton.

Examples

Generate practice file for problem 23:

.\scripts\new_practice.bat 23

Include all solution variants (when the reference has multiple):

.\scripts\new_practice.bat 23 --all-solutions

Preview generated content without writing:

.\scripts\new_practice.bat 23 --dry-run

Troubleshooting

python not found / wrong Python

new_practice.bat uses python from your PATH. If you have a project virtual environment, activate it first, or run the equivalent python -m ... using the correct interpreter.

"Failed to fetch problem ..."

CodeGen needs the problem slug to compute the filename. If it cannot resolve the slug locally, it may try to fetch it (depending on your DataSource/cache setup). Ensure your environment is configured to access LeetCode data, or generate the reference solution first.