---
title: "Set up Python for use with Nexus"
canonical: "https://help.vicon.com/space/Nexus212/11247869/Set%20up%20Python%20for%20use%20with%20Nexus"
format: markdown
---
The Nexus API is supplied as a Python package called 
    *
        **viconnexusapi**
    *
     and is automatically installed with Nexus. The build of Python installed within Nexus is Python 2. You can run the Python SDK for Nexus in a Python 3 environment as well as in a Python 2 environment.


For more information, see the following topics.

> Macro (scroll-only)
> 
> > Macro (toc)

## Configure Python for scripting with Nexus


    **To set up Python to work with Nexus:**


1. Click **Start**, point to **All Programs** and then start to type Python.
2. Click the Python symbol.
3. To automatically configure Python for scripting with Nexus, at the command prompt, enter the following:

##### **UsingViconNexusAPI.py**

```python
from viconnexusapi import ViconNexus
vicon = ViconNexus.ViconNexus()
```

or

##### **UsingViconNexusAPI2.py**

```python
import viconnexusapi
vicon = viconnexusapi.ViconNexus.ViconNexus()
```


      



The Python installed with Nexus contains the API version shipped with that version. However, if you install the package into another Python distribution, you are responsible for installing the appropriate version.

For information on how to access the help provided on the relevant Python commands, see [Python commands for use with Nexus](https://vicon-help.atlassian.net/wiki/spaces/Nexus212/pages/11242718). For more information about how to use Python, see [https://www.python.org/about/gettingstarted/](https://www.python.org/about/gettingstarted/).

> ⚠️ **Important**   
> ⚠️ If you disconnect your Ethernet cable and turn off wifi, when you enter a Python command, the following error may be displayed:   
> ⚠️ `Host Application is not connected, unable to retrieve command list`   
> ⚠️ This is because Python connects to Nexus over TCP/IP and if you are working entirely offline, Python and Nexus cannot connect.   
> ⚠️ To solve this issue, install the Microsoft Loopback Adapter. For instructions on how to do this, see [Install the Microsoft loopback adapter](#InstallLBAdapter).

> Macro (scroll-pagebreak)

## Install the Nexus API into other Python distributions

The build of Python (Python 2) installed within Nexus automatically installs the *viconnexusapi* package as part of Nexus. A script is also available with both the 32- and 64-bit installers, which installs the package into the system Python distribution. You can also directly install the package into any other Python distributions that you have installed.

##### **Installing_viconnexusapi**

```powershell
cd "C:\Program Files (x86)\Vicon\Nexus2.12\SDK\Win32\Python"
# install the api into the system python
./install_vicon_nexus_api.bat
# install the api into a specific python distribution
<path to user python> -m pip install ./viconnexusapi
```

The advanced modeling scripts are provided as a package called *viconnexusutils *and are available in the same way as *viconnexusapi*, except that these scripts are not automatically installed. This is because they have additional dependencies that cannot be guaranteed to be present and must be downloaded by *pip*.

## Launch the required Python

The shell launched by the python operation is either the Python distribution shipped with Nexus or your default Python (as determined by the PATH variable).

If the Python distribution shipped with Nexus is launched, the API package is automatically available for import, and additional scripts (eg, *ViconSetPython32Path.py*) are no longer required.

If you choose to use a Python that is different from the installed Nexus distribution, you can use a new advanced option to select the command used to launch Python. The options for this are **python.exe** or **py.exe**:

- If you have only a Python 2 **or** a Python 3 installation in the path, **python.exe** launches that version of Python.
- If you have both versions and the *pylauncher* utility, **py.exe** launches either Python 2 or Python 3, depending on a shebang comment at the start of the launched script.

### CGM2 Python version

CGM2 launches using the version of Python 2 installed with Nexus. 


    > Macro (anchor)




## Install the Microsoft loopback adapter


    **To install the Microsoft loopback adapter on Windows 10:**


1. Right-click the Windows **Start** menu icon and select**Device Manager** (or use your preferred method of opening the Device Manager).
2. In the **Device Manager**, click the **Action** menu and then select**Add legacy hardware**.
3. On the welcome screen, click**Next**.
4. In the Add Hardware screen, select **Install the hardware that I manually select from a list** and then click **Next**.
5. In the next screen, scroll down the **Common hardware types** list, select**Network adapters** and then click **Next**.
6. From the **Manufacturer** list, select**Microsoft**, and then select**Microsoft KM-TEST Loopback Adapter**card model and click **Next**.
7. In the next screen, click **Next**.
8. Click **Finish**.