liuguiyu just i didnt see this in the online doc ...
I admit it's a little hidden, but in my defence there's a paragraph in http://tinydb.readthedocs.io/en/latest/usage.html#queries (at the bottom of the section)
The second, traditional way of constructing queries is as follows:
>>> from tinydb import where
>>> db.search(where('field') == 'value')
Using where('field') is a shorthand for the following code:
>>> db.search(Query()['field'] == 'value')