diff --git a/osxphotos/_constants.py b/osxphotos/_constants.py
index c521e29e..b110e72a 100644
--- a/osxphotos/_constants.py
+++ b/osxphotos/_constants.py
@@ -1,3 +1,7 @@
+"""
+Constants used by osxphotos 
+"""
+
 # which Photos library database versions have been tested
 # Photos 2.0 (10.12.6) == 2622
 # Photos 3.0 (10.13.6) == 3301
diff --git a/osxphotos/photoinfo.py b/osxphotos/photoinfo.py
index 3ee45804..3601026f 100644
--- a/osxphotos/photoinfo.py
+++ b/osxphotos/photoinfo.py
@@ -1,3 +1,9 @@
+"""
+PhotoInfo class
+Represents a single photo in the Photos library and provides access to the photo's attributes
+PhotosDB.photos() returns a list of PhotoInfo objects
+"""
+
 import json
 import logging
 import os.path
diff --git a/osxphotos/photosdb.py b/osxphotos/photosdb.py
index 12488ed3..c2a2979b 100644
--- a/osxphotos/photosdb.py
+++ b/osxphotos/photosdb.py
@@ -1,3 +1,8 @@
+"""
+PhotosDB class
+Processes a Photos.app library database to extract information about photos
+"""
+
 import logging
 import os.path
 import pathlib