Added get_system_library_path

README.md

@@ -129,6 +129,12 @@ if __name__ == "__main__":
 
 ## Module Interface
 
+### Utility Functions
+
+#### ```get_system_library_path()```
+
+**MacOS 10.15 Only** Return path to System Photo Library as string.  On MacOS version < 10.15, raises Exception.
+
 ### PhotosDB
 
 #### Open the default Photos library

osxphotos/__init__.py

@@ -109,7 +109,33 @@ def _get_resource_loc(model_id):
 
     return folder_id, file_id
 
+def get_system_library_path():
+    """ return the path to the system Photos library as string """
+    """ only works on MacOS 10.15+ """
+    """ on earlier versions, will raise exception """
+    ver, major, minor = _get_os_version()
+    if int(major) < 15:
+        raise Exception("get_system_library_path not implemented for MacOS < 10.15",major)
 
+    plist_file = Path(
+        str(Path.home())
+        + "/Library/Containers/com.apple.photolibraryd/Data/Library/Preferences/com.apple.photolibraryd.plist"
+    )
+    if plist_file.is_file():
+        with open(plist_file, "rb") as fp:
+            pl = plistload(fp)
+    else:
+        logging.warning(f"could not find plist file: {str(plist_file)}")
+        return None
+
+    photospath = pl["SystemLibraryPath"]
+
+    if photospath is not None:
+        return photospath
+    else:
+        logging.warning("Could not get path to Photos database")
+        return None
+        
 class PhotosDB:
     def __init__(self, dbfile=None):
         """ create a new PhotosDB object """