Python Runner

Run arbitrary Python code inside an isolated Micromamba env
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Overview

This node executes arbitrary Python code inside an isolated environment managed by Micromamba, a lightweight package manager. It allows users to specify the exact Python version and any pip-style package requirements, runs the provided Python script, and returns the standard output of that script.

Common scenarios where this node is beneficial include:

  • Running custom Python scripts that require specific Python versions or dependencies without affecting the host system.
  • Testing or prototyping Python code snippets within an n8n workflow.
  • Automating data processing or analysis tasks using Python libraries installed on demand.

For example, you could use this node to run a Python script that processes JSON input, uses pandas for data manipulation (installed via requirements), and outputs results back into the workflow.

Properties

Name Meaning
Python Version Exact Python version string to use, e.g., "3.9", "3.10.14", "3.11".
Requirements List of pip-style package requirements, one per line, to install in the environment.
Python Code The Python source code to execute; the node returns its standard output (stdout).
Keep Environment Boolean flag indicating whether to keep the created Micromamba environment after execution.

Output

The node outputs a single JSON object with one field:

  • output: A string containing the trimmed standard output (stdout) produced by the executed Python script.

No binary data output is produced by this node.

Example output JSON structure:

{
  "output": "Result from the Python script"
}

Dependencies

  • Micromamba: The node requires Micromamba to create isolated Python environments dynamically. If Micromamba is not found on the system, the node attempts to download and install it automatically.
  • Python: The specified Python version must be available via Micromamba.
  • pip packages: Any packages listed in the "Requirements" property are installed inside the created environment before running the script.
  • System utilities: The node uses shell commands like wget, tar, and rm for managing Micromamba installation and environment cleanup.

No additional n8n credentials or environment variables are required.

Troubleshooting

  • Micromamba not found or failed to install: The node tries to install Micromamba if missing, but this requires network access and certain system utilities (wget, tar). Ensure these are available and accessible.
  • Python version unavailable: Specifying a Python version not supported by Micromamba will cause environment creation to fail. Use valid version strings.
  • Package installation errors: Invalid or conflicting package requirements can cause pip install failures. Verify the requirements syntax and compatibility.
  • Script execution errors: Errors in the Python code itself will propagate as node operation errors. Check your Python code for syntax or runtime issues.
  • Large output buffer exceeded: The node sets a max buffer size for stdout (10 MB). Extremely large outputs may cause errors.
  • Environment cleanup: If "Keep Environment" is false, the environment is deleted after execution. If set true, environments accumulate and consume disk space.

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