> ## Documentation Index
> Fetch the complete documentation index at: https://training-docs.cerebras.ai/llms.txt
> Use this file to discover all available pages before exploring further.

#  Modulenotfounderror 

## ModuleNotFoundError: No module named \<’\_bz2’, ‘\_sqlite3’>

Users may experience a `ModuleNotFoundError` for some Python provided packages on their local machine.

### Observed Error

This line of code

```bash theme={null}
import bz2
```

gives error:

```bash theme={null}
Traceback (most recent call last):
import bz2
File "/usr/local/lib/python3.8/bz2.py", line 19, in <module>
    from _bz2 import BZ2Compressor, BZ2Decompressor
ModuleNotFoundError: No module named '_bz2'
```

### Explanation

Python installation was built from source but didn’t have all necessary system packages installed for full Python build.

### Work around

Install *bzip2-devel* and *sqlite-devel* and rebuild Python, or download a pre-built Python binary.

## ModuleNotFoundError: No module named \<…>

Users may experience a `ModuleNotFoundError` for some Python packages that are available on their local machine.

### Explanation

The [Custom Worker Container Workflow](../../fundamentals/import-user-dependencies-in-cerebras) provides seamless support for importing user-specific dependency packages in the Python environments into the Cerebras appliances. In case of failure, a fallback policy has also been enabled to mount the site packages from the user node Python virtual environment to the worker environment via a predefined NFS-based cluster volume.

### Work around

If you observe a `ModuleNotFoundError`, you can disable the Custom Worker Container Workflow by following the instructions [here](../../fundamentals/import-user-dependencies-in-cerebras), and follow the R1.8 approach:

* pip install the packages in virtual environment

* Copy the custom package directory from `venv/lib/python3.8/site-packages/<package_name>` to a NFS-mountable location for the Cerebras cluster. Only copy the custom packages, not the entire virtual environment.

* Make sure to add this location to the `--mount_dirs` command line argument and the corresponding parent location to the `--python_paths` command line argument when calling run.py.