[Feature Request] Array Element Overrides from dotlist via getitem syntax

[apsdehal]

Currently, OmegaConf supports overriding as training_parameters.lr_steps.1=500 for overriding a specific element of an array. This is not intuitive and we should support proper getitem syntax for array element overrides.

training_parameters.lr_steps[1]=500 should be supported.

[omry]

Blocked on #445

[Jasha10]

If I am not mistaken, this issue is resolved:

>>> training_parameters = OmegaConf.create({"lr_steps": [1000,800,100,75]})
>>> training_parameters
{'lr_steps': [1000, 800, 100, 75]}
>>> training_parameters.lr_steps[1]
800
>>> training_parameters.lr_steps[1] = 500
>>> training_parameters
{'lr_steps': [1000, 500, 100, 75]}

[odelalleau]

If I am not mistaken, this issue is resolved:

No, that's because the way it's phrased can be misleading. training_parameters.lr_steps[1]=500 is not meant to be read as a Python statement, but as a command line override as would be used in Hydra for instance. In OmegaConf, it's actually more about the select / update functions that assume the key is dot-separated (search for split(".") in the code)

[omry]

In [3]: cfg = OmegaConf.create({"a" : {"b": [1,2,3]}})

In [4]: cfg
Out[4]: {'a': {'b': [1, 2, 3]}}

In [5]: OmegaConf.select(cfg, "")
Out[5]: {'a': {'b': [1, 2, 3]}}

In [6]: OmegaConf.select(cfg, "a")
Out[6]: {'b': [1, 2, 3]}

In [7]: OmegaConf.select(cfg, "a.b")
Out[7]: [1, 2, 3]

In [8]: OmegaConf.select(cfg, "a.b.0")
Out[8]: 1

What would be good is to support:

OmegaConf.select(cfg, "a.b[0]")

In fact, we can support it for regular dict access as well:

OmegaConf.select(cfg, "[a][b][0]")

[omry]

This should probably cover the interpolation syntax as well, so it can be too much for 2.1:

list:
 - a
 - b 
item0: ${list.0}  # a, current syntax
item1: ${list[1]} # b, new syntax

[dasturge]

Hi, I found this issue when trying to figure out how to do just that. Can you point me to documentation I missed or, can I request documentation of this feature?

[Jasha10]

Hi @dasturge,

Take a look at the docs on Config node interpolation.

Also, there are usage examples in the OmegaConf.select docs and the OmegaConf.update docs.