py2store.examples.last_key_inserted

showing how to add the knowledge of the ‘last key inserted’ to stores

py2store.examples.last_key_inserted.remember_last_key_written_to(cls=None, *, only_if_new_key=False, name=None, same_name_as_class=False)

A decorator to get a class that remembers the last key that was written to. Note that this is the last key that THIS STORE wrote to, not the last key that was written to the DB.

Some would say “it’s not thread-safe”, but that statement might be overkill. See the code to see what you should or should not expect.

Parameters

• cls – The class you want to decorate (omit if you want to make a decorator factory instead)

• only_if_new_key – If by “last written to” we mean “last created” (i.e. only keep track if the key is NEW, not if we just updated the value)

• name – The name you want the decorated class to have

• same_name_as_class – If you want to use the name of the decorated class itself.

Returns

A decorated class (if the class was given), or a class decorator (if cls=None).

>>> def test(s):
...     # test:
...     s['hello'] = 'you'
...     assert s._last_key_written_to == 'hello'
...     s['goodbye'] = 'them'
...     assert s._last_key_written_to == 'goodbye'
...     s['hello'] = 'you'
...     assert s._last_key_written_to == 'hello'
...
>>>
>>> S = remember_last_key_written_to(dict)
>>> s = S()
>>> test(s)
>>>
>>> # Use as decorator factory
>>> @remember_last_key_written_to
... class SS(dict):
...     pass
...
>>>
>>> ss = SS()
>>> test(ss)
>>>
>>> SSS = remember_last_key_written_to(dict, only_if_new_key=True)
>>> sss = SSS()
>>> assert sss._last_key_written_to is None
>>> sss['hi'] = 'there'
>>> sss._last_key_written_to
'hi'
>>> sss[3] = .1415
>>> sss._last_key_written_to
3
>>> sss['hi'] = 'this key already exists!'
>>> sss._last_key_written_to  # so this should still be 3
3