History

History is a light weight mapping backed by sqlite which remember the history of values. The intent is for tracking relatively complex configurations.

Examples

The interface is very simple and can be accessed either via [] like a dictionary or

In [1]: from history import History

In [2]: fn = '/tmp/testing'

In [3]: hist = History(fn)

In [4]: hist['key'] = 'foo'

In [5]: hist['key']
Out[5]: 'foo'

via put and past

In [6]: hist.put('k', 'bar')

In [7]: hist.past('k')
Out[7]: 'bar'

Using past you can extract past values

In [8]: hist['key'] = 'baz'

In [9]: hist['key'] = 'buz'

In [10]: hist['key'] = 'aardvark'

In [11]:

In [11]: hist['key']
Out[11]: 'aardvark'

In [12]: hist.past('key', 1)
Out[12]: 'buz'

In [13]: hist.past('key', 2)
Out[13]: 'baz'

In [14]: hist.past('key', 3)
Out[14]: 'foo'

All MutableMapping methods except del and pop work.

Known limitation

The keys are stored in the underlying sqlite table via the hash of their string representation. This means things like:

hist[{'a': 123, 'b': 456}] = 'cat'

will work without error, but in python 3 will only get the same hash half of the time. Only use keys which have stable and unique string representations.

The values are stored via a json blob, thus only values which can be converted to json can be stored (no numpy arrays currently).

h.del and h.pop do not work (yet). Just need to write the sql query to delete them.