[Property values] Add append_values method for modifying values

[hkchekc]

Refer to Issue #382.

[coveralls]

Coverage increased (+0.08%) to 89.427% when pulling 6f9e745 on hkchekc:val_append into d849bda on G-Node:master.

[jgrewe]

I guess we need a test case for that :)

[achilleas-k]

I was wondering if there was a more pythonic way to do this and I realised that, since values is a property with a getter and a setter, anything we do on the property directly should just work, assuming the operation works on the type returned by the getter.

So this doesn't work:

prop.values.append(10)

because values is a tuple and tuples don't have an append method, but this does

prop.values += (10,)

because you can concatenate tuples with +.

It's essentially equivalent to

v = prop.values
v += (10,)
prop.values = v

and our values setter already takes care of resizing when necessary.

nixpy/nixio/property.py

Line 273 in ef2637c

self._h5dataset.shape = np.shape(vals)

I suppose it might still be useful for users to have an append_values() method. Though I think it could be simplified to just a + operation on the values property. Perhaps we should also call it extend() if it's going to support multi-value append. Could do both.

EDIT: The append/extend methods could probably check if the new data is the same type (or can be upgraded to the type) of the existing data. If users use a += though, it's up to them to keep the types in mind, which I think is fine, since concatenating values of different types is equivalent to assigning a mixed-value tuple to the property.values property and should follow the same rules.

[achilleas-k]

Looks good. Thanks!