python: cleanup the __nonzero__ implementations

Cleanup the code, reword the docstring and use the same implementation
in the Threads, Tags and Messages classes.

__nonzero__ implements truth value testing. If __nonzero__ is not
implemented, the python runtime would fall back to `len(..) > 0` thus
exhausting the iterator.

Signed-off-by: Justus Winter <4winter@informatik.uni-hamburg.de>

1 files changed, 9 insertions, 5 deletions

diff --git a/bindings/python/notmuch/messages.py b/bindings/python/notmuch/messages.py
index 251fa3a..59ef40a 100644
--- a/bindings/python/notmuch/messages.py
+++ b/bindings/python/notmuch/messages.py
@@ -172,11 +172,15 @@ class Messages(object):
     next = __next__ # python2.x iterator protocol compatibility
 
     def __nonzero__(self):
-        """
-        :return: True if there is at least one more thread in the
-            Iterator, False if not."""
-        return self._msgs is not None and \
-            self._valid(self._msgs) > 0
+        '''
+        Implement truth value testing. If __nonzero__ is not
+        implemented, the python runtime would fall back to `len(..) >
+        0` thus exhausting the iterator.
+
+        :returns: True if the wrapped iterator has at least one more object
+                  left.
+        '''
+        return self._msgs and self._valid(self._msgs)
 
     _destroy = nmlib.notmuch_messages_destroy
     _destroy.argtypes = [NotmuchMessagesP]