[Tutor] Nested for loops, possibly?

[Bob Williams]

Hi,

My script is running under Python 3.4.1 on a 64bit openSUSE linux system. It is a backup script making calls to rsync and btrfs-tools, and backing up several different paths. Here is the script, my question follows below:

**Code**
import datetime
import glob
import os, os.path
import subprocess
import sys

if not os.getuid() == 0:
    print("\n*** This script must be run as root. ***\n")
    sys.exit()

mnt_path = "/home/bob/A3"
    
subprocess.call(["mount", "LABEL=backup", mnt_path])
if not os.path.ismount(mnt_path):
    print("\nBackup drive is not mounted\nCheck if it is attached.\n")
    sys.exit()
else:
    print("\nBackup drive mounted at", mnt_path, "\n")

src_path = "/home/bob"

today = datetime.datetime.now()
fname = today.strftime("%y-%m-%d_%H-%M")

doc_retain = datetime.timedelta(days=90)
pic_retain = datetime.timedelta(days=90)
misc_retain = datetime.timedelta(days=90)
etc_retain = datetime.timedelta(days=30)
mus_retain = datetime.timedelta(days=30)
web_retain = datetime.timedelta(days=30)
rep_retain = datetime.timedelta(days=30)

doc_srcpath = os.path.join(src_path, "Documents")
pic_srcpath = os.path.join(src_path, "Pictures")
misc_srcpath = src_path
etc_srcpath = "/etc"
music_srcpath = os.path.join(src_path, "music")
www_srcpath = "/srv/www"
repo_srcpath = os.path.join(src_path, "download")

doc_syncpath = os.path.join(mnt_path, "documents")
pic_syncpath = os.path.join(mnt_path, "pictures")
misc_syncpath = os.path.join(mnt_path, "miscellaneous")
etc_syncpath = os.path.join(mnt_path, "etc")
music_syncpath = os.path.join(mnt_path, "music")
www_syncpath = os.path.join(mnt_path, "www")
repo_syncpath = os.path.join(mnt_path, "repo")

doc_snappath = os.path.join(mnt_path, "docsnaps", fname)
pic_snappath = os.path.join(mnt_path, "picsnaps", fname)
misc_snappath = os.path.join(mnt_path, "miscsnaps", fname)
etc_snappath = os.path.join(mnt_path, "etcsnaps", fname)
music_snappath = os.path.join(mnt_path, "musicsnaps", fname)
www_snappath = os.path.join(mnt_path, "wwwsnaps", fname)
repo_snappath = os.path.join(mnt_path, "reposnaps", fname)

doc_snaplist = glob.glob(mnt_path + "/docsnaps/*")
pic_snaplist = glob.glob(mnt_path + "/picsnaps/*")
misc_snaplist = glob.glob(mnt_path + "/miscsnaps/*")
etc_snaplist = glob.glob(mnt_path + "/etcsnaps/*")
music_snaplist = glob.glob(mnt_path + "/musicsnaps/*")
www_snaplist = glob.glob(mnt_path + "/wwwsnaps/*")
repo_snaplist = glob.glob(mnt_path + "/reposnaps/*")

def do_sync(source, dest):
    subprocess.call(['rsync', '-av', '--safe-links', '--delete-excluded', '-F', source, dest])
    print("\n")

def create_snaps(newsnap, snapdest):
    subprocess.call(['btrfs', 'subvolume', 'snapshot', newsnap, snapdest])
    print("\n")

def expire_snaps(snaplist, today, expiry_interval):
    x = 0
    print("\nDeleting snapshots older than", str(expiry_interval)[:7], "...")
    for i in range(0, len(snaplist)):
        snap_date = datetime.datetime.strptime(snaplist[i][-14:], "%y-%m-%d_%H-%M")
        if today - snap_date >= expiry_interval:
            subprocess.call(['btrfs', 'subvolume', 'delete', snaplist[i]])
            x += 1
    if x == 0:
        print("... No snapshots older than", str(expiry_interval)[:7], "found - nothing to do.")
    else:
        print("...", x, "snapshot(s) deleted.")
    print("\n")

def main():
    print("Backing up ", src_path, "/Documents\n", sep='')
    do_sync(doc_srcpath, doc_syncpath)
    create_snaps(doc_syncpath, doc_snappath)
    print("Documents backup completed.")
    expire_snaps(doc_snaplist, today, doc_retain)

    print("Backing up ", src_path, "/Pictures\n", sep='')
    do_sync(pic_srcpath, pic_syncpath)
    create_snaps(pic_syncpath, pic_snappath)
    print("Pictures backup completed.")
    expire_snaps(pic_snaplist, today, pic_retain)

    print("Backing up Miscellaneous files\n")      
    do_sync(misc_srcpath, misc_syncpath)
    create_snaps(misc_syncpath, misc_snappath)
    print("Miscellaneous backup completed.")
    expire_snaps(misc_snaplist, today, misc_retain)

    print("Backing up /etc\n")
    do_sync(etc_srcpath, etc_syncpath)
    create_snaps(etc_syncpath, etc_snappath)
    print("Backup of /etc completed.")
    expire_snaps(etc_snaplist, today, etc_retain)

    print("Backing up ", src_path, "/music\n", sep='')
    do_sync(music_srcpath, music_syncpath)
    create_snaps(music_syncpath, music_snappath)
    print("Music backup completed.")
    expire_snaps(music_snaplist, today, mus_retain)

    print("Backing up Web server\n")
    do_sync(www_srcpath, www_syncpath)
    create_snaps(www_syncpath, www_snappath)
    print("Web server backup completed.")
    expire_snaps(www_snaplist, today, web_retain)

    print("Backing up Download repository\n")
    do_sync(repo_srcpath, repo_syncpath)
    create_snaps(repo_syncpath, repo_snappath)
    print("Download repository backup completed.")
    expire_snaps(repo_snaplist, today, rep_retain)

    print("\nAll backups completed.")
    print("\nUnmounting backup drive.\n")
    subprocess.call(['umount', mnt_path])
    print("\n>>> Please power down the Quad external drive enclosure <<<\n")

if __name__ == "__main__":
    main()
**/Code**

I would like to reduce all those repeated calls to do_sync() in main(), for example, to one by putting the *_srcpath and *_*syncpath variables into lists (eg. source_list and sync_list) and using a for loop to get the first item out of each list, then the second item, etc. Something like:

for i in range(0, len(source_list)):
    for j in range(0, len(sync_list)):
        do_sync(source_list[i], sync_list[j])

but this will get all the values of sync_list[j] for each value of source_list[i], which is not what I want.

I hope this is clear enough to see my problem? I realise that the print statements will need some work, I'm just trying to get the functionality working.

TIA

Bob
-- 
Bob Williams
System:  Linux 3.16.7-7-desktop
Distro:  openSUSE 13.2 (x86_64) with KDE Development Platform: 4.14.3
Uptime:  06:00am up 7:55, 3 users, load average: 0.16, 0.05, 0.06