I have this script for creating SQLite backups, and I was wondering whether you'd have any suggestions on how to improve this. I was thinking that maybe it should create the backupdir if it doesn't exist, but not sure if it's necessarily better.
Besides functionality/performance tips, any styling/formatting tips are also much appreciated.
#!/usr/bin/env python"""This script creates a timestamped database backup,and cleans backups older than a set number of dates""" from __future__ import print_functionfrom __future__ import unicode_literalsimport argparseimport sqlite3import shutilimport timeimport osDESCRIPTION = """ Create a timestamped SQLite database backup, and clean backups older than a defined number of days """# How old a file needs to be in order# to be considered for being removedNO_OF_DAYS = 7def sqlite3_backup(dbfile, backupdir): """Create timestamped database copy""" if not os.path.isdir(backupdir): raise Exception("Backup directory does not exist: {}".format(backupdir)) backup_file = os.path.join(backupdir, os.path.basename(dbfile) + time.strftime("-%Y%m%d-%H%M%S")) connection = sqlite3.connect(dbfile) cursor = connection.cursor() # Lock database before making a backup cursor.execute('begin immediate') # Make new backup file shutil.copyfile(dbfile, backup_file) print ("\nCreating {}...".format(backup_file)) # Unlock database connection.rollback()def clean_data(backup_dir): """Delete files older than NO_OF_DAYS days""" print ("\n------------------------------") print ("Cleaning up old backups") for filename in os.listdir(backup_dir): backup_file = os.path.join(backup_dir, filename) if os.stat(backup_file).st_ctime < (time.time() - NO_OF_DAYS * 86400): if os.path.isfile(backup_file): os.remove(backup_file) print ("Deleting {}...".format(ibackup_file))def get_arguments(): """Parse the commandline arguments from the user""" parser = argparse.ArgumentParser(description=DESCRIPTION) parser.add_argument('db_file', help='the database file that needs backed up') parser.add_argument('backup_dir', help='the directory where the backup' 'file should be saved') return parser.parse_args()if __name__ == "__main__": args = get_arguments() sqlite3_backup(args.db_file, args.backup_dir) clean_data(args.backup_dir) print ("\nBackup update has been successful.")Note: Code works in both Python 2 and Python 3.
- 2\$\begingroup\$Note that SQLite has anOnline Backup API, though unfortunately it does not appear to be available through Python.\$\endgroup\$200_success– 200_success2015-01-26 20:39:11 +00:00CommentedJan 26, 2015 at 20:39
- 1\$\begingroup\$On my Linux box with Python 2.7.14
st_ctimereturns the same value for all files in the backup folder. I have to change it tost_mtimeto fix the "cleaning backup" part\$\endgroup\$Sergey Minsky– Sergey Minsky2018-10-16 19:24:39 +00:00CommentedOct 16, 2018 at 19:24 - \$\begingroup\$
Lock database before making a backup; what happens if the database is already locked?\$\endgroup\$user5359531– user53595312018-11-14 22:44:01 +00:00CommentedNov 14, 2018 at 22:44 - \$\begingroup\$@SergeySventitski So this code is only python 3 compliant?\$\endgroup\$dfhwze– dfhwze2019-08-03 20:09:23 +00:00CommentedAug 3, 2019 at 20:09
3 Answers3
This looks like a pretty nice script to me.
I was thinking that maybe it should create the backup dir if it doesn't exist, but not sure if it's necessarily better.
I don't think there's a universal answer to that,it's your call how you want the script to behave.It depends on your use whether you need the script to create a backup directory if it doesn't exist,or if you want to avoid it creating directories at unintended locations.A compromise might be to add a-p flag likemkdir has to "create parents".
Not that it really matters,but I think it should be slightly more efficient,and more natural to flip these conditions:
if os.stat(backup_file).st_ctime < (time.time() - NO_OF_DAYS * 86400): if os.path.isfile(backup_file):
That is:
if os.path.isfile(backup_file): if os.stat(backup_file).st_ctime < (time.time() - NO_OF_DAYS * 86400):You seem to be followingPEP8 for the most part,with few exceptions:
- Don't put a space before parentheses, as in
print (something) - Put two empty lines in front of function definitions
There's no need to repeat yourself by definingDESCRIPTION (and in fact your strings have gotten out of sync). Just reuse the program's docstring:
def get_arguments(): """Parse the commandline arguments from the user""" parser = argparse.ArgumentParser(description=__doc__) …
- \$\begingroup\$Does
__doc__there refer to the function docstring or the module docstring?\$\endgroup\$jpmc26– jpmc262017-10-11 19:11:22 +00:00CommentedOct 11, 2017 at 19:11
Found a little typo in your code when executing it in a test project:
print ("Deleting {}...".format(ibackup_file))should be
print("Deleting {}...".format(backup_file))Also you should use a consistence naming (e.g. backupdir vs. backup_dir).If got the feeling you made decision based on avoiding over 80 (using the underscore in the variable name ends in a line with 81 letters). Try to avoid doing changes like this. Instead make a new line for the parameters of a function or something like this.
I would suggest to store the elapse time in an own variable:
elapse_time = time.time() - NO_OF_DAYS * 86400and
if os.stat(backup_file).st_ctime < elapse_time:
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