running a selection uses a different path than runnning the whole file

When I run a the whole file with the script package, the location of the file is in the path used. But when I run script on a selection of the file, its location is not in the path. As an example, compare the output of the code below when running the whole file vs running all lines selected.

```
import sys
print(sys.path)
```

This is particularly problematic when working with local packages, which won't be imported.