preinst is in python-central 0.6.17ubuntu1.
This file is a maintainer script. It is executed when installing (*inst) or removing (*rm) the package.
The actual contents of the file can be viewed below.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23  | #! /bin/sh
set -e
case "$1" in
    install|upgrade)
	mkdir -p /var/lib/pycentral
	echo '# the presence of this file allows calling pkgremove on upgrade' \
	    > /var/lib/pycentral/pkgremove
    ;;
    abort-upgrade)
    ;;
    *)
        echo "preinst called with unknown argument \`$1'" >&2
        exit 1
    ;;
esac
exit 0
 |