First, set your editor (such as PythonWin or Wing) in Geoprocessing > Geoprocessing Options. Next, in the Catalog window, right-click your tool and click Edit.
Geoprocessing doesn't read your script code until you click OK on the script tool dialog box or press ENTER while in the Python window.
A common workflow when working with Python script tools is as follows:
- Edit your script (using PythonWin or IDLE, for example) and save your changes, but don't exit the editing application.
- Run the script tool.
- If need be, make more code changes, saving your edits but not exiting the editing application.
- Run the script tool again.
- When you're satisfied that your script is working correctly, exit the editing application.