title: Use SQLite as a key:value store
body: <p>As suggested in comments from <a href="https://stackoverflow.com/questions/47233562/key-value-store-in-python-for-possibly-100-gb-of-data-without-client-server">Key: value store in Python for possibly 100 GB of data, without client/server</a> and in other questions, SQLite could totally be used as a persistent key:value store.</p>
  
  <p>How would you define a class (or just wrapper functions) such that using a key:value store with SQLite would be as simple as:</p>
  
  <pre><code>kv = Keyvaluestore('/test.db')
  kv['hello'] = 'hi'        # set
  print(kv['hello'])         # get
  print('blah' in kv)        # answer: False because there's no key 'blah' in the store
  kv.close()
  </code></pre>
  
  <p>?</p>