/usr/bin/python2.6 can be specified for a Python script. This option corresponds to using %pre --interpreter /usr/bin/python2.6 in your kickstart file.
arping, awk, basename, bash, bunzip2, bzcat, cat, chattr, chgrp, chmod, chown, chroot, chvt, clear, cp, cpio, cut, date, dd, df, dirname, dmesg, du, e2fsck, e2label, echo, egrep, eject, env, expr, false, fdisk, fgrep, find, fsck, fsck.ext2, fsck.ext3, ftp, grep, gunzip, gzip, hdparm, head, hostname, hwclock, ifconfig, insmod, ip, ipcalc, kill, killall, less, ln, load_policy, login, losetup, ls, lsattr, lsmod, lvm, md5sum, mkdir, mke2fs, mkfs.ext2, mkfs.ext3, mknod, mkswap, mktemp, modprobe, more, mount, mt, mv, nslookup, openvt, pidof, ping, ps, pwd, readlink, rm, rmdir, rmmod, route, rpm, sed, sh, sha1sum, sleep, sort, swapoff, swapon, sync, tail, tar, tee, top, touch, true, tune2fs, umount, uniq, vconfig, vi, wc, wget, xargs, zcat.
Important
%pre command. It is added for you.
Note