How to add to the PYTHONPATH in Windows, so it finds my modules/packages?

In Windows, you can add to the PYTHONPATH environment variable to make sure that Python can find your modules and packages. There are a few different ways to do this, depending on how you have Python installed and which version you're using.

Using the command prompt

Open the command prompt and use the set command to add to the PYTHONPATH environment variable.
```
set PYTHONPATH=%PYTHONPATH%;C:\path\to\your\module
```
You can also use the setx command, which allows you to set environment variables system-wide and persist the changes, if you want to make the changes persist after you close the command prompt
```
setx PYTHONPATH %PYTHONPATH%;C:\path\to\your\module
```
Using the environment variables settings

You can also add to the PYTHONPATH environment variable using the environment variables settings:
- Press the Windows key + R, type sysdm.cpl, and press Enter.
- Click on the Advanced tab and then click on Environment Variables.
- Under User variables (or System variables if you have admin rights) scroll down and find the variable named PYTHONPATH. If it doesn't exist, click New to create it.
- Add the path to your module or package to the end of the variable value, separated by a semicolon. For example: C:\path\to\your\module;
Using an IDE

If you're using an IDE such as IDLE, PyCharm, or Spyder, you may be able to add to the PYTHONPATH directly through the IDE's settings. The option to add to PYTHONPATH can be found in a different place depending on the IDE that you are using.

Once you've added the path to your module or package to the PYTHONPATH environment variable, you can test whether Python can find your module by running the following command in the Python interpreter or in the command prompt:

Test whether Python can find your module

import sys
print(sys.path)

This will print a list of all the directories that Python is currently searching for modules and packages. If your directory is in that list, you've set the PYTHONPATH correctly.

Alternatively, you can append the path directly in your script before importing your modules:

Append path before importing a module

import sys
sys.path.append(r"C:\path\to\your\module")

Also, if you are using the Anaconda distribution, it's worth checking the conda documentation on how to add new paths to the Python interpreter on Windows.