diff --git a/.gitignore b/.gitignore
index 85c18d3..02517cd 100644
--- a/.gitignore
+++ b/.gitignore
@@ -19,6 +19,7 @@ pip-log.txt
 # Unit test / coverage reports
 .coverage
 .tox
+.cache
 
 # sqlite databases
 *.sqlite
diff --git a/sqlitedict.py b/sqlitedict.py
index f6b47d7..07343c6 100755
--- a/sqlitedict.py
+++ b/sqlitedict.py
@@ -168,7 +168,7 @@ def __exit__(self, *exc_info):
         self.close()
 
     def __str__(self):
-        return "SqliteDict(%s)" % (self.conn.filename)
+        return "SqliteDict(%s)" % (self.filename)
 
     def __repr__(self):
         return str(self)  # no need of something complex
@@ -233,12 +233,18 @@ def __setitem__(self, key, value):
         self.conn.execute(ADD_ITEM, (key, encode(value)))
 
     def __delitem__(self, key):
+        if self.flag == 'r':
+            raise RuntimeError('Refusing to delete from read-only SqliteDict')
+
         if key not in self:
             raise KeyError(key)
         DEL_ITEM = 'DELETE FROM %s WHERE key = ?' % self.tablename
         self.conn.execute(DEL_ITEM, (key,))
 
     def update(self, items=(), **kwds):
+        if self.flag == 'r':
+            raise RuntimeError('Refusing to update read-only SqliteDict')
+
         try:
             items = [(k, encode(v)) for k, v in items.items()]
         except AttributeError:
@@ -253,6 +259,9 @@ def __iter__(self):
         return self.iterkeys()
 
     def clear(self):
+        if self.flag == 'r':
+            raise RuntimeError('Refusing to clear read-only SqliteDict')
+
         CLEAR_ALL = 'DELETE FROM %s;' % self.tablename  # avoid VACUUM, as it gives "OperationalError: database schema has changed"
         self.conn.commit()
         self.conn.execute(CLEAR_ALL)
@@ -289,6 +298,9 @@ def close(self, do_log=True):
 
     def terminate(self):
         """Delete the underlying database file. Use with care."""
+        if self.flag == 'r':
+            raise RuntimeError('Refusing to terminate read-only SqliteDict')
+
         self.close()
 
         if self.filename == ':memory:':
@@ -303,7 +315,13 @@ def terminate(self):
 
     def __del__(self):
         # like close(), but assume globals are gone by now (do not log!)
-        self.close(do_log=False)
+        try:
+            self.close(do_log=False)
+        except Exception:
+            # prevent error log flood in case of multiple SqliteDicts
+            # closed after connection lost (exceptions are always ignored
+            # in __del__ method.
+            pass
 
 # Adding extra methods for python 2 compatibility (at import time)
 if major_version == 2:
diff --git a/tests/test_core.py b/tests/test_core.py
index b3476ae..78a4419 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -26,6 +26,9 @@ def test_as_str(self):
         db = sqlitedict.SqliteDict()
         # exercise
         db.__str__()
+        # test when db closed
+        db.close()
+        db.__str__()
 
     def test_as_repr(self):
         """Verify SqliteDict.__repr__()."""
@@ -94,17 +97,38 @@ def test_readonly(self):
         fname = norm_file('tests/db/sqlitedict-override-test.sqlite')
         orig_db = sqlitedict.SqliteDict(filename=fname)
         orig_db['key'] = 'value'
+        orig_db['key_two'] = 2
         orig_db.commit()
         orig_db.close()
 
         readonly_db = sqlitedict.SqliteDict(filename=fname, flag = 'r')
         self.assertTrue(readonly_db['key'] == 'value')
+        self.assertTrue(readonly_db['key_two'] == 2)
 
         def attempt_write():
             readonly_db['key'] = ['new_value']
 
-        with self.assertRaises(RuntimeError):
-            attempt_write()
+        def attempt_update():
+            readonly_db.update(key = 'value2', key_two = 2.1)
+
+        def attempt_delete():
+            del readonly_db['key']
+
+        def attempt_clear():
+            readonly_db.clear()
+
+        def attempt_terminate():
+            readonly_db.terminate()
+
+        attempt_funcs = [attempt_write, 
+                         attempt_update, 
+                         attempt_delete,
+                         attempt_clear,
+                         attempt_terminate]
+
+        for func in attempt_funcs:
+            with self.assertRaises(RuntimeError):
+                func()
 
     def test_overwrite_using_flag_w(self):
         """Re-opening of a database with flag='w' destroys only the target table."""