ModuleNotFoundError: No module named 'simpleeval' in ComfyUI

If ComfyUI logs ModuleNotFoundError: No module named 'simpleeval', the server may still start, but math expression nodes can fail to register.

In the SEO Lab portable repair, the missing module appeared in comfy_extras\nodes_math.py. Installing simpleeval removed the remaining IMPORT FAILED line for that node file.

.\python_embeded\python.exe -s -m pip show simpleeval
.\python_embeded\python.exe -s -m pip install simpleeval
.\python_embeded\python.exe -s -c "import simpleeval; print('import ok')"
.\python_embeded\python.exe -s ComfyUI\main.py --windows-standalone-build

What The Log Looks Like

Typical startup lines:

ModuleNotFoundError: No module named 'simpleeval'
Cannot import ...\ComfyUI\comfy_extras\nodes_math.py module for custom nodes: No module named 'simpleeval'
IMPORT FAILED: nodes_math.py

The path matters. In the lab this was a built-in extra node file, not a random third-party plugin folder.

Quick Diagnosis

Step 1: Install In The Python That Launches ComfyUI

Windows portable:

.\python_embeded\python.exe -s -m pip install simpleeval

Manual venv:

python -m pip install simpleeval

Step 2: Verify The Import

Run the import check before restarting:

.\python_embeded\python.exe -s -c "import simpleeval; print(simpleeval.__name__)"

For a manual venv:

python -c "import simpleeval; print(simpleeval.__name__)"

Step 3: Restart And Check Node Availability

Restart ComfyUI and read the startup log:

.\python_embeded\python.exe -s ComfyUI\main.py --windows-standalone-build

The original No module named 'simpleeval' line should be gone. If you are doing a deeper portable repair, check /object_info after restart to confirm expected node registration.

What Not To Do

• do not reinstall ComfyUI just because one built-in extra node failed
• do not install into system Python if ComfyUI uses python_embeded
• do not ignore the error if your workflow uses math expression nodes
• do not keep installing unrelated packages after the server starts; repair the first missing node and verify

Related Guides

• Repair ComfyUI Portable Dependencies One Missing Module At A Time
• No module named 'pydantic_settings' in ComfyUI
• No module named 'spandrel' in ComfyUI
• Fix No module named errors in ComfyUI
• Plugin Missing Module Warning: When It Is Safe to Ignore

Source References

• Windows portable SEO Lab repair, May 18, 2026: No module named 'simpleeval' blocked ComfyUI\comfy_extras\nodes_math.py
• Same lab cleanup action: pip install simpleeval removed the IMPORT FAILED: nodes_math.py line
• simpleeval on PyPI