add efficient `__contains__`

tests/tests_tqdm.py

@@ -1973,3 +1973,14 @@ def test_closed():
         for i in trange(9, file=our_file, miniters=1, mininterval=0):
             if i == 5:
                 our_file.close()
+
+
+def test_contains(capsys):
+    """Test __contains__ doesn't iterate"""
+    with tqdm(_range(9)) as t:
+        assert 9 not in t
+        assert all(i in t for i in range(9))
+    out, err = capsys.readouterr()
+    assert not out
+    assert '  0%' in err
+    assert '100%' not in err

tqdm/std.py

@@ -1131,6 +1131,10 @@ class tqdm(Comparable):
             else self.iterable.__length_hint__() if hasattr(self.iterable, "__length_hint__")
             else getattr(self, "total", None))
 
+    def __contains__(self, item):
+        contains = getattr(self.iterable, '__contains__', None)
+        return contains(item) if contains is not None else item in self.__iter__()
+
     def __enter__(self):
         return self