fix: Address issues #44, #45, #50 for v2.3.0 release

- Add LICENSE file with dual Artistic-1.0 / GPL-1.0+ license (fixes #44)
- Remove outdated VERSION = 1.9 comment (fixes #45)
- Add UniqueList class to prevent duplicate keywords/contacts/categories (fixes #50)
- Deduplicate list fields both on append and at save time
- Bump version to 2.3.0

Author: James Campbell

CHANGELOG.md

@@ -1,3 +1,15 @@
+## 2.3.0 (2025-12-02)
+
+### Bug Fixes
+- **Issue #50**: Fixed keywords and other list fields to prevent duplicate values (deduplicates on append and save)
+- **Issue #45**: Removed outdated VERSION = 1.9 comment from code
+
+### New Features
+- **Issue #44**: Added LICENSE file with dual Artistic-1.0 / GPL-1.0+ license
+- Added `UniqueList` class for list fields that automatically prevents duplicates
+
+---
+
 ## 2.2.0 (2025-10-02)
 
 ### Bug Fixes

LICENSE

@@ -0,0 +1,20 @@
+IPTCInfo3 - IPTC metadata extraction and modification for Python
+
+Copyright (C) 2000-2004 Josh Carter <josh@multipart-mixed.com>
+Copyright (C) 2004-2008 Tamas Gulacsi <gthomas@gthomas.hu>
+Copyright (C) 2008-2025 James Campbell
+
+DUAL LICENSE
+
+This software is dual-licensed. You may choose either:
+
+1. The Artistic License 1.0
+   https://opensource.org/licenses/Artistic-1.0
+
+2. The GNU General Public License v1.0 or later
+   https://www.gnu.org/licenses/old-licenses/gpl-1.0.en.html
+
+You may use, modify, and distribute this software under the terms of
+either license, at your option.
+
+Full license texts available at the URLs above.

iptcinfo3.py

@@ -14,7 +14,6 @@
 # it under the terms of the Artistic License or the GNU General Public
 # License (GPL). You may choose either license.
 #
-# VERSION = '1.9';
 """
 IPTCInfo - Python module for extracting and modifying IPTC image meta-data
 """
@@ -27,7 +26,7 @@
 from struct import pack, unpack
 import json
 
-__version__ = '2.2.0'
+__version__ = '2.3.0'
 __author__ = 'Gulácsi, Tamás'
 __updated_by__ = 'Campbell, James'
 
@@ -524,6 +523,17 @@ def collect_adobe_parts(data):
 c_charset_r = {v: k for k, v in c_charset.items()}
 
 
+class UniqueList(list):
+    """A list that prevents duplicate values on append/extend."""
+    def append(self, value):
+        if value not in self:
+            super().append(value)
+
+    def extend(self, values):
+        for v in values:
+            self.append(v)
+
+
 class IPTCData(dict):
     """Dict with int/string keys from c_listdatanames"""
     def __init__(self, diction={}, *args, **kwds):
@@ -608,9 +618,9 @@ class IPTCInfo:
 
     def __init__(self, fobj, force=False, inp_charset=None, out_charset=None):
         self._data = IPTCData({
-            'supplemental category': [],
-            'keywords': [],
-            'contact': [],
+            'supplemental category': UniqueList(),
+            'keywords': UniqueList(),
+            'contact': UniqueList(),
         })
         self._fobj = fobj
         self._force = force
@@ -956,10 +966,11 @@ def packedIIMData(self):
                 out.append(pack("!BBBH", tag, record, dataset, len(value)))
                 out.append(value)
             else:
+                seen = set()
                 for v in map(bytes, value):
-                    if v is None or len(v) == 0:
+                    if v is None or len(v) == 0 or v in seen:
                         continue
-
+                    seen.add(v)
                     out.append(pack("!BBBH", tag, record, dataset, len(v)))
                     out.append(v)
 

pyproject.toml

@@ -4,7 +4,7 @@ build-backend = "hatchling.build"
 
 [project]
 name = "IPTCInfo3"
-version = "2.2.0"
+version = "2.3.0"
 description = "Extract and modify IPTC metadata from JPEG images"
 readme = "README.rst"
 license = { text = "Artistic-1.0 OR GPL-1.0-or-later" }