Modified for pip version 18 and above:
pip list | tail -n +3 | awk '{print $1}' | xargs pip show | grep -E 'Location:|Name:' | cut -d ' ' -f 2 | paste -d ' ' - - | awk '{print $2 "/" tolower($1)}' | xargs du -sh 2> /dev/null | sort -hr
This command shows pip packages, sorted by descending order of sizes.