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+---
+title: 'Automatically clean up "Previous Mobile Applications"'
+date: 2015-06-27T21:19:59-07:00
+date-display: June 27, 2015
+---
+iTunes keeps a "Previous Mobile Applications" folder of questionable value, which always annoys me. It eats into disk space and wastes syncing/backup cycles and bandwidth; you can easily find horror stories online about [100GB+ PMA folders](http://forums.macrumors.com/threads/5-years-of-deleted-iphone-apps-accumulated-in-my-itunes-library.1781676/#post-19749496). The value? You might be able to roll back to an earlier version, or restore an app pulled from the App Store. Really? I never had that need in my life[^disclosure]; have you? Worst of all, there should be a periodic clean up option — just like how deleted mail are automatically purged after one month, but the option is missing.
+
+[^disclosure]: Full disclosure: unlike many people, I'm not very obsessed with my phone, and I only have about two dozen third-party apps.
+
+Therefore, I wrote a trivial Python script to do the periodic cleanup. Feel free to grab my script below (also available at <http://git.io/previous-mobile-applications>) to save a few minutes of hacking. It should be plugged into a daily or weekly or monthly cron job (or the equivalent), and it writes data to `~/.local/share/itunes/previous-mobile-applications.json` by default. To customize, just modify the global constants.
+
+```python
+#!/usr/bin/env python3
+
+"""Periodically clean up "Previous Mobile Applications" of iTunes."""
+
+import arrow
+import datetime
+import json
+import os
+import sys
+
+OFFENDING_DIR = os.path.expanduser("~/Music/iTunes/iTunes Media/Mobile Applications/Previous Mobile Applications")
+STORAGE_DIR = os.path.expanduser("~/.local/share/itunes")
+STORAGE_FILE = os.path.join(STORAGE_DIR, "previous-mobile-applications.json")
+
+DELETE_AFTER = datetime.timedelta(days=7)
+
+def load_storage():
+    """Load stored dictionary of seen apps from STORAGE_FILE.
+
+    Returns
+    -------
+    seen_app_dict : dict
+        Dictionary of (app_filename, first_seen_date) key-value pairs,
+        where app_filename is str, and last_seen_date is datetime.date.
+
+    """
+    os.makedirs(STORAGE_DIR, mode=0o700, exist_ok=True)
+    try:
+        with open(STORAGE_FILE, encoding="utf-8") as fp:
+            serializable_seen_app_dict = json.load(fp)
+            return {app_filename: arrow.get(serialized_first_seen_date).date()
+                    for app_filename, serialized_first_seen_date in serializable_seen_app_dict.items()}
+    except OSError:
+        return {}
+
+def write_storage(seen_app_dict):
+    """Write the dictionary of seen apps to STORAGE_FILE.
+
+    Parameters
+    ----------
+    seen_app_dict : dict
+        See the return format of load_storage().
+
+    Returns
+    -------
+    0 or 1
+        Return code indicating success or failure.
+
+    """
+    # convert datetime.time to str (ISO 8601)
+    serializable_seen_app_dict = {app_filename: first_seen_date.isoformat()
+                                  for app_filename, first_seen_date in seen_app_dict.items()}
+    os.makedirs(STORAGE_DIR, mode=0o700, exist_ok=True)
+    try:
+        with open(STORAGE_FILE, mode="w", encoding="utf-8") as fp:
+            json.dump(serializable_seen_app_dict, fp, indent=2, sort_keys=True)
+        return 0
+    except OSError as err:
+        sys.stderr.write("error: failed to write to '%s': %s" % (STORAGE_FILE, str(err)))
+        return 1
+
+def main():
+    """Main.
+
+    Returns
+    -------
+    0 or 1
+        Return code indicating success or failure.
+
+    """
+    if not os.path.isdir(OFFENDING_DIR):
+        # good, you don't have that junk
+        return 0
+
+    today = datetime.date.today()
+    seen_app_dict = load_storage()
+    current_app_list = os.listdir(OFFENDING_DIR)
+
+    # boot already disappeared apps
+    for app in [app for app in seen_app_dict if app not in current_app_list]:
+        seen_app_dict.pop(app)
+
+    # add newly appeared apps
+    for app in [app for app in current_app_list if app not in seen_app_dict]:
+        seen_app_dict[app] = today
+
+    # delete expired apps
+    returncode = 0
+    newly_deleted_apps = []
+    for app in seen_app_dict:
+        if today >= seen_app_dict[app] + DELETE_AFTER:
+            app_path = os.path.join(OFFENDING_DIR, app)
+            try:
+                os.remove(app_path)
+                newly_deleted_apps.append(app)
+            except OSError as err:
+                sys.stderr.write("error: failed to remove '%s': %s" % (app_path, str(err)))
+                returncode = 1
+
+    for app in newly_deleted_apps:
+        seen_app_dict.pop(app)
+
+    # write data to disk
+    returncode |= write_storage(seen_app_dict)
+
+    return returncode
+
+if __name__ == "__main__":
+    exit(main())
+```