Raise an IOError with a relevant error message when trying to access the metadata of an image that has not been read() yet.

Previously, a misleading AttributeError would be raised (this was a regression from the 0.1.x series).

1 files changed, 11 insertions, 5 deletions

diff --git a/src/pyexiv2/metadata.py b/src/pyexiv2/metadata.py
index a121286..8adeab6 100644
--- a/src/pyexiv2/metadata.py
+++ b/src/pyexiv2/metadata.py
@@ -61,7 +61,7 @@ class ImageMetadata(MutableMapping):
         self.filename = filename
         if filename is not None:
             self.filename = filename.encode(sys.getfilesystemencoding())
-        self._image = None
+        self.__image = None
         self._keys = {'exif': None, 'iptc': None, 'xmp': None}
         self._tags = {'exif': {}, 'iptc': {}, 'xmp': {}}
         self._exif_thumbnail = None
@@ -86,9 +86,15 @@ class ImageMetadata(MutableMapping):
         :type buffer: string
         """
         obj = cls(None)
-        obj._image = libexiv2python._Image(buffer, len(buffer))
+        obj.__image = libexiv2python._Image(buffer, len(buffer))
         return obj
 
+    @property
+    def _image(self):
+        if self.__image is None:
+            raise IOError('Image metadata has not been read yet')
+        return self.__image
+
     def read(self):
         """
         Read the metadata embedded in the associated image.
@@ -96,9 +102,9 @@ class ImageMetadata(MutableMapping):
         the metadata (an exception will be raised if trying to access metadata
         before calling this method).
         """
-        if self._image is None:
-            self._image = self._instantiate_image(self.filename)
-        self._image._readMetadata()
+        if self.__image is None:
+            self.__image = self._instantiate_image(self.filename)
+        self.__image._readMetadata()
 
     def write(self, preserve_timestamps=False):
         """